System And Method For Controlling Operation Of A Two-Stroke Engine Having A Turbocharger

ABSTRACT

A method and system for controlling operation of a two-stroke engine having a turbocharger includes the two-stroke engine comprising an electronically controlled exhaust valve. A throttle position sensor generates a throttle position signal corresponding to a position of a throttle plate of a throttle. A boost box is coupled to the two-stroke engine. A boost box pressure sensor is coupled to the boost box and generates a boost box pressure signal corresponding to a pressure within the boost box. A controller is coupled to the boost box pressure signal controlling a position of the electronically controlled exhaust valve in response to the boost box pressure signal and the throttle position signal.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a divisional of U.S. application Ser. No.17/145,298, filed Jan. 9, 2021, which claims priority to non-provisionalapplication of 62/960,414, filed Jan. 13, 2020. This applicationincorporates the disclosures of U.S. application Ser. No. 16/691,995filed Nov. 22, 2019, U.S. application Ser. No. 16/696,198 filed Nov. 26,2019, U.S. application Ser. No. 16/691,097 filed Nov. 21, 2019, U.S.application Ser. No. 16/692,336 filed Nov. 22, 2019, U.S. applicationSer. No. 16/692,470 filed Nov. 22, 2019, U.S. application Ser. No.16/692,628 filed Nov. 22, 2019, U.S. application Ser. No. 16/692,724filed Nov. 22, 2019, U.S. application Ser. No. 16/692,795 filed Nov. 22,2019, and U.S. Provisional Application No. 62/690,388 filed on Jan. 13,2020. The entire disclosures of the above applications are incorporatedherein by reference.

FIELD

The present disclosure relates to a vehicle engine and, moreparticularly, to a method of operating the engine with an electronicallycontrolled exhaust valve and turbocharger.

BACKGROUND

This section provides background information related to the presentdisclosure which is not necessarily prior art.

A vehicle, such as a snowmobile, generally includes an engine assembly.The engine assembly is operated with the use of fuel to generate powerto drive the vehicle. The power to drive a snowmobile is generallygenerated by a combustion engine that drives pistons and a connectedcrankshaft. Two-stroke snowmobile engines are highly tuned, and highspecific power output engines that operate under a wide variety ofconditions.

Vehicle manufacturers are continually seeking ways to improve the poweroutput for engines. Turbochargers have been used together withtwo-stroke engines to provide increased power output. However, improvingthe packaging and performance of a turbocharged two-stroke engine isdesirable.

SUMMARY

This section provides a general summary of the disclosures, and is not acomprehensive disclosure of its full scope or all of its features.

In one aspect of the disclosure a system for controlling operation of atwo-stroke engine having a turbocharger includes the two-stroke enginecomprising an electronically controlled exhaust valve. A throttleposition sensor generates a throttle position signal corresponding to aposition of a throttle plate of a throttle. A boost box is coupled tothe two-stroke engine. A boost box pressure sensor is coupled to theboost box and generates a boost box pressure signal corresponding to apressure within the boost box. A controller is coupled to the boost boxpressure signal controlling a position of the electronically controlledexhaust valve in response to the boost box pressure signal and thethrottle position signal.

In another aspect of the disclosure, a method or controlling operationof a two-stroke engine having a turbocharger includes generating athrottle position signal corresponding to a position of a throttle platefrom a throttle position sensor, generating a boost box pressure signalcorresponding to a pressure within a boost box and controlling aposition of an electronically controlled exhaust valve in response tothe boost box pressure signal and the throttle position signal.

In another aspect of the disclosure, a system for controlling an enginehaving a turbocharger includes a boost pressure sensor generating aboost pressure signal, a barometric pressure sensor generating abarometric pressure signal and a controller coupled to the boostpressure sensor and the barometric pressure sensor. The controller isprogrammed to determine an offset between the boost pressure signal andthe barometric pressure signal, when the offset is outside a tolerancerange, display an indicator.

In still another aspect of the disclosure, a method for controlling anengine having a turbocharger includes generating a boost pressuresignal, generating a barometric pressure signal and a controllerprogrammed to determine an offset between the boost pressure signal andthe barometric pressure signal, display an indicator when the offset isoutside a tolerance range.

In another aspect of the disclosure, a method includes determining anexhaust bypass valve position from an exhaust bypass valve positionsignal and controlling a fuel and ignition system based on the exhaustbypass valve position signal.

Further areas of applicability will become apparent from the descriptionprovided herein. The description and specific examples in this summaryare intended for purposes of illustration only and are not intended tolimit the scope of the present disclosure.

DRAWINGS

FIG. 1 is a perspective view of a snowmobile.

FIG. 2 is an exploded view of the snowmobile of FIG. 1.

FIGS. 2A and 2B are enlarged exploded views of FIG. 2.

FIG. 3 is a block diagram of the engine of FIG. 2.

FIG. 4 is an exploded view of the engine of FIG. 3.

FIG. 5A is a perspective view of a turbocharger according to the presentdisclosure.

FIG. 5B is a side view of the turbocharger FIG. 5A.

FIG. 5C is a cutaway view of the turbine housing of the turbocharger ofFIG. 5A.

FIG. 5D is a partial cross-sectional view of the turbine housing of theturbocharger of FIG. 5A.

FIG. 5E is a cutaway view of the turbocharger having the diverter valvein a position closing off the first scroll.

FIG. 5F is a partial cutaway view of the turbocharger having thediverter valve in a neutral position.

FIG. 5G is a partial cutaway view of the turbocharger having thediverter valve in a position closing off the second scroll.

FIG. 5H is a partial cutaway view of an alternate valve for controllingflow to the scrolls in a partially open position.

FIG. 5I is a partial cutaway view of the valve in FIG. 5H in a closedposition.

FIG. 5J is a partial cutaway view of another alternate valve forcontrolling flow to one of the scrolls in a closed position.

FIG. 5K is a partial cutaway view of the valve in FIG. 5J in a partiallyopen position.

FIG. 6A is a cross-sectional view of an exhaust gas bypass valve.

FIG. 6B is the exhaust bypass valve of FIG. 6A in a first open position.

FIG. 6C is the exhaust bypass valve of FIG. 6A in a second openposition.

FIG. 6D is the exhaust bypass valve of FIG. 6A in a third open position.

FIG. 6E is the exhaust bypass valve of FIG. 6A in a fully open position.

FIG. 6F is a perspective view of the exhaust bypass valve with anactuator arm.

FIG. 6G is an end view of the exhaust bypass valve in the positionillustrated in FIG. 6E.

FIG. 6H is a block diagrammatic view of a system for operating theexhaust bypass valve of FIG. 6A.

FIG. 6I is a perspective view of an exhaust bypass valve and divertervalve controlled by a common actuator.

FIG. 6J is a perspective view of a wastegate actuator according to anexample of the present disclosure.

FIG. 6K is a block diagrammatic view of a wastegate actuator and acoupler.

FIG. 6L is another example of a coupler for a wastegate.

FIG. 6M is a perspective view of a method for joining a coupler.

FIG. 6N is a perspective view of a turbocharger system with exhaustbypass valve coupled via flexible shaft to an electronic actuator.

FIG. 6O is a perspective view of a rotating member of the coupler FIG.6N.

FIG. 6P is a perspective view of a flexible coupler for a wastegatecoupled to a wastegate actuator coupled to a bracket formed with theturbocharger.

FIG. 6Q is a perspective view of a clamp for clamping a wastegateactuator and wastegate to a tuned pipe.

FIG. 7A is a schematic view of a system for bypassing exhaust gas.

FIG. 7B is a schematic view of a second example for bypassing exhaustgas.

FIG. 7C is a schematic view of a third example of bypassing exhaust gas.

FIG. 7D is a schematic view of a fourth example of bypassing exhaustgas.

FIG. 7E is a diagrammatic representation of an engine system includingexhaust bypass for increasing the stability of a two-stroke engine.

FIG. 7F is a diagrammatic representation of an engine assemblycomprising a second example of increasing the stability of a two stokeengine.

FIG. 7G is a diagrammatic representation of an engine assembly having athird example of an exhaust bypass valve for increasing the stability ofa two-stroke engine alternate positions of the exhaust bypass valve areilluminated.

FIG. 7H is a diagrammatic representation of a control valve within astinger of the exhaust system of a normally aspirated two-stroke engineassembly.

FIG. 7I is a diagrammatic representation of a control valve within asilencer.

FIG. 7J is a diagrammatic representation of a control valve within asub-chamber of a silencer.

FIG. 7K is a schematic view of another example of bypassing exhaust gasusing a silencer and supplemental silencer with a common wall.

FIG. 7L is a schematic view of two part muffler with a common walltherebetween having two inputs and a single exhaust pipe receivingexhaust gasses from both parts of the muffler.

FIG. 7M is a schematic view of a pipe from a turbocharger and pipe froma wastegate joined at a Y-joint before the silencer.

FIG. 7N is a schematic view of the pipe coupled to a flange prior toentering the silencer wherein the flange and joint may all be formed asone component.

FIG. 7O is a schematic view of the engine assembly, the tuned pipe andthe turbocharger wherein the effective area of cross-sectional flow ofthe wastegate or exhaust bypass valve is greater than the cross-sectionflow area of the stinger.

FIG. 8A is a schematic view of a system for bypassing the compressor ofa turbocharged engine to provide airflow to the engine.

FIG. 8B is a rear side of the boost box of FIG. 8A.

FIG. 8C is a left side view of the boost box of FIG. 8A.

FIG. 8D is a front side view of the boost box of FIG. 8A.

FIG. 8E is a right side view of the boost box of FIG. 8A.

FIG. 8F is an enlarged view of the one-way valve of FIG. 8A.

FIG. 8G is a side view of an engine compartment having the boost boxoriented so that the one-way valve is located rearwardly.

FIG. 8H is a side view of a boost box coupled to a duct.

FIG. 8I is a side view of the boost box coupled to a channel integrallyformed with a fuel tank.

FIG. 9A is a block diagrammatic view of a system for controlling anexhaust bypass valve.

FIG. 9B is a flowchart of a method for controlling the exhaust gasbypass valve.

FIG. 9C is a plot of boost error versus time for a plurality of signalsused for updating the exhaust gas bypass valve position.

FIG. 9D is a plot of the calculation multiplier versus boost error.

FIG. 9E is a graph illustrating the absolute pressure and changes overvarious altitudes.

FIG. 9F is a flowchart of a method for controlling an exhaust gas bypassvalve to increase power or stability of a two-stroke engine.

FIG. 9G is a block diagrammatic view of a first example of the exhaustgas bypass valve position control module.

FIG. 9H is a flowchart of a method for operating the exhaust gas bypassvalve in response to an idle and acceleration event.

FIG. 10A is a side view of a rotor of a turbocharger.

FIG. 10B is an end view of the rotor of FIG. 10A.

FIG. 10C is a diagrammatic representation of the exducer area.

FIG. 10D is a plot of the ratio of exhaust gas bypass valve or bypassvalve area to exducer area for known four stroke engines, two strokeengines and the present example.

FIG. 11A is a method for controlling the exhaust valve of the engine.

FIG. 11B is a diagrammatic representation of the gains for the wastegateposition.

FIG. 11C is a flowchart of a method for changing the wastegate position.

FIG. 12A is a block diagrammatic view of a system for allowing the userto select a boost mode.

FIG. 12B is a flowchart of a method for allowing a user to select aboost mode.

FIG. 12C is a flowchart of the control strategy of FIG. 12B.

FIG. 13A is a flowchart of a method for preventing overboost in anengine.

FIG. 13B is a flowchart of a method for preventing overtemperature in anengine.

FIG. 14A is a flowchart of a method for controlling the wastegate basedupon deceleration.

FIG. 14B is a signal diagram that shows the wastegate opening slightlybased upon an overboost condition.

FIG. 14C is a signal diagram that shows driving the wastegate more fullyopened based upon deceleration.

FIGS. 15A and 15B are flowcharts of a method for controlling the enginein an acceleration mode.

FIG. 15C is a signal diagram showing the engine when controlled for anacceleration mode.

FIG. 16A is a front view of a connecting rod according to the presentdisclosure.

FIG. 16B is a cross-sectional view of the connecting rod.

FIG. 16C is a force diagram of connecting rods with and without theinertia reducing holes.

FIG. 16D is an inertia diagram of the connecting rods with and withoutthe inertia reducing holes.

FIG. 17 is a perspective view of roller bearings according to thepresent disclosure,

FIG. 18 is a block diagrammatic view of a system for controlling theengine in further detail relative to a sensor diagnostic mode, awastegate initialization mode, an exhaust valve controller and fueladjustment module.

FIG. 19 is a flowchart of a method for controlling an engine based uponthe absolute air box pressure.

FIG. 20 is a method for checking the range of a wastegate upon startup.

FIG. 21 is a flowchart of a method for monitoring the current of thewastegate upon startup.

FIG. 22 is a flowchart of a method of controlling fueling and ignitionbased upon the wastegate position.

FIG. 23 is a signal diagram of the engine speed uncorrected andcorrected relative to the wastegate position and the throttle positionand the boost pressure.

FIG. 24 is a flowchart of a method for determining the differencebetween barometric pressure and the boost sensor.

FIG. 25 is a diagrammatic view of a diagnostic threshold for use withthe method of FIG. 24.

DETAILED DESCRIPTION

Examples will now be described more fully with reference to theaccompanying drawings. Although the following description includesseveral examples of a snowmobile application, it is understood that thefeatures herein may be applied to any appropriate vehicle, such asmotorcycles, all-terrain vehicles, utility vehicles, moped, scooters,etc. The examples disclosed below are not intended to be exhaustive orto limit the disclosure to the precise forms disclosed in the followingdetailed description. Rather, the examples are chosen and described sothat others skilled in the art may utilize their teachings. The signalsset forth below refer to electromagnetic signals that communicate data.

Referring now to FIGS. 1 and 2, one example of an exemplary snowmobile10 is shown. Snowmobile 10 includes a chassis 12, an endless beltassembly 14, and a pair of front skis 20. Snowmobile 10 also includes afront-end 16 and a rear-end 18.

The snowmobile 10 also includes a seat assembly 22 that is coupled tothe chassis assembly 12. A front suspension assembly 24 is also coupledto the chassis assembly 12. The front suspension assembly 24 may includehandlebars 26 for steering, shock absorbers 28 and the skis 20. A rearsuspension assembly 30 is also coupled to the chassis assembly 12. Therear suspension assembly 30 may be used to support the endless belt 14for propelling the vehicle. An electrical console assembly 34 is alsocoupled to the chassis assembly 12. The electrical console assembly 34may include various components for displaying engine conditions (i.e.,gauges) and for electrically controlling the snowmobile 10.

The snowmobile 10 also includes an engine assembly 40. The engineassembly 40 is coupled to an intake assembly 42 and an exhaust assembly44. The intake assembly 42 is used for providing fuel and air into theengine assembly 40 for the combustion process. Exhaust gas leaves theengine assembly 40 through the exhaust assembly 44. The exhaust assembly44 includes the exhaust manifold 45 and tuned pipe 47. An oil tankassembly 46 is used for providing oil to the engine for lubricationwhere it is mixed directly with fuel. In other systems oil and fuel maybe mixed in the intake assembly. A drivetrain assembly 48 is used forconverting the rotating crankshaft assembly from the engine assembly 40into a potential force to use the endless belt 14 and thus thesnowmobile 10. The engine assembly 40 is also coupled to a coolingassembly 50.

The chassis assembly 12 may also include a bumper assembly 60, a hoodassembly 62 and a nose pan assembly 64. The hood assembly 62 is movableto allow access to the engine assembly 40 and its associated components.

Referring now to FIGS. 3 and 4, the engine assembly 40 is illustrated infurther detail. The engine assembly 40 is a two-stroke engine thatincludes the exhaust assembly 44 that includes an exhaust manifold 45,tuned pipe 47, an exhaust valve 49, an exhaust port actuator 49A andexhaust silencer 710. The exhaust valve 49 may be electronicallycontrolled to achieve various states of opening and closing.

The engine assembly 40 may include spark plugs 70 which are coupled to aone-piece cylinder head cover 72. The cylinder head cover 72 is coupledto the cylinder 74 with twelve bolts which is used for housing thepistons 76 to form a combustion chamber 78 therein. The cylinder 74 ismounted to the engine upper crankcase 80.

The fuel and ignition system 82 that forms part of the engine assembly40, includes fuel lines 84 and fuel injectors 86 and the controlloer todetermine fuel quantities and ignition timing. The fuel lines 84 providefuel to the fuel injectors 86 which inject fuel, in this case, into aport in the cylinder adjacent to the pistons 76. In other cases, aninjection may take place adjacent to the piston, into a boost box(detailed below) or into the throttle body. An intake manifold 88 iscoupled to the engine upper crankcase 80. The intake manifold 88 is influidic communication with the throttle body 90. Air for the combustionprocesses is admitted into the engine through the throttle body 90 whichmay be controlled directly through the use of an accelerator pedal orhand operated lever or switch. A throttle position sensor 92 is coupledto the throttle to provide a throttle position signal corresponding tothe position of the throttle plate 94 to an engine controller discussedfurther herein.

The engine upper crankcase 80 is coupled to lower crankcase 100 andforms a cavity for housing the crankshaft 102. The crankshaft 102 hasconnecting rods 104 which are ultimately coupled to the pistons 76. Themovement of the pistons 76 within the combustion chamber 78 causes arotational movement at the crankshaft 102 by way of the connecting rods104. The crankcase may have openings or vents 106 therethrough.

The system is lubricated using oil lines 108 which are coupled to theoil injectors 110 and an oil pump 112.

The crankshaft 102 is coupled to a generator flywheel 118 and having astator 120 therein. The flywheel 118 has crankshaft position sensors 122that aid in determining the positioning of the crankshaft 102. Thecrankshaft position sensors 122 are aligned with the teeth 124 and areused when starting the engine, as well as being used to time theoperation of the injection of fuel during the combustion process. Astator cover 126 covers the stator 120 and flywheel 118.

Discussed below are various features of the engine assembly 40 used inthe snowmobile 10. Each of the features relate to the noted sectionheadings set forth below. It should be noted that each of these featurescan be employed either individually or in any combination with theengine assembly 40. Moreover, the features discussed below will utilizethe reference numerals identified above, when appropriate, or othercorresponding reference numerals as needed. Again, as noted above, whilethe engine assembly 40 is a two-stroke engine that can be used with thesnowmobile 10, the engine assembly 40 can be used with any appropriatevehicles and the features discussed below may be applied to four-strokeengine assemblies as well.

The engine assembly 40 also includes an exhaust manifold 45 that directsthe exhaust gases from the engine. The exhaust manifold 45 is in fluidcommunication with a tuned pipe 47. The tuned pipe 47 is specificallyshaped to improve the performance and provide the desired feedback tothe engine assembly 40. The tuned pipe 47 is in communication with astinger 134. The tuned pipe 47 has a bypass pipe 136 coupled thereto.The bypass pipe 136 has an exhaust gas bypass valve 138 used forbypassing some or all of the exhaust gases from being directed to aturbocharger 140. Details of the turbocharger 140 are set forth in thefollowing Figures.

Referring now to FIGS. 5A-5G, the turbocharger 140 includes a turbineportion 510 and a pump or compressor portion 512. The turbine portion510 and the compressor portion 512 have a common shaft 521 that extendsthere between. That is, the rotational movement within the turbineportion 510 caused from the exhaust gases rotate a turbine wheel 520which in turn rotates the shaft 521 which, in turn, rotates a compressorwheel 519. The compressor portion 512 includes an inlet 514 and anoutlet 516. Movement of the compressor wheel 519 causes inlet air fromthe inlet 514 to be pressurized and output through the outlet 516 of thehousing 518.

The turbine portion 510 includes a turbine wheel 520 with housing 522.The housing 522 includes a turbine inlet 524 and a turbine outlet 526.The inlet 524 receives exhaust gas through the tuned pipe 47 and thestinger 134 as illustrated above. The exhaust gases enter the inlet 524and are divided between a first scroll 528 and a second scroll 530. Ofcourse, more than two scrolls may be implemented in a system. Thescrolls 528, 530 may also be referred to as a volute. Essentially thefirst scroll 528 and the second scroll 530 start off with a widecross-sectional area and taper to a smaller cross-sectional area nearthe turbine wheel. The reduction in cross-sectional area increases thevelocity of the exhaust gases which in turn increases the speed of theturbine wheel 520. Ultimately, the rotation of the turbine wheel 520turns the compressor wheel 519 within the compressor portion 512 by wayof a common shaft 521. The size of the first scroll 528 and the secondscroll 530 may be different. The overall area to radius (A/R) ratio ofthe scrolls may be different. The first scroll 528 has a first end 528Aand a second end 528B and the second scroll has a second first end 530Aand a second end 530B. The first ends 528A, 530A are adjacent to theturbine inlet 524. The second ends 528B, 530B are adjacent to theturbine wheel 520 within the housing 522. The volume of the first scroll528 and second scroll 530 may be different. The cross-sectional openingadjacent to the turbine wheel 520 may be different between the scrolls.

The first scroll 528 and the second scroll 530 are separated by aseparation wall 532. The separation wall 532 separates the first scroll528 from the second scroll 530. The separation wall 532 may extend fromthe first end 528A of the first scroll 528 and the first end 530A of thesecond scroll 530 to the second end 528B, 530B of the respectivescrolls.

The turbine portion 510 includes an exhaust gas diverter valve 540mounted adjacent to the separation wall 532. The exhaust gas divertervalve 540 is used to selectively partially or fully close off either thefirst scroll 528 or the second scroll 530. A valve seat 542A is locatedadjacent to the first scroll 528. A second valve seat 542B is locatedadjacent to the second scroll 530. Either one of the valve seats 542A,542B receive the exhaust gas diverter valve 540 when the exhaust gasdiverter valve 540 is in a completely closed position. The valve seats542A, 542B may be recesses or grooves that are formed within the housing522. The valve seats 542A, 542B form a surface that receives an edge 541of the exhaust gas diverter valve 540 so that when exhaust gases pushthe exhaust gas diverter valve 540 into the scroll outer wall, the valveseats 542A, 542B provide a counter force. The edge 541 is the end of thevalve 540 opposite a pivot pin 544. The valve seats 542A, 542B may becircumferentially formed within each of the first scroll 528 and thesecond scroll 530. The seal between the valve 540 may be on the edge 541or on the surface of the valve 540 on each side of the edges 541.

The pivot pin 544 which extends across the turbine inlet 524 toselectively separate or close off the first scroll 528 or the secondscroll 530. A partial closing of either the first scroll 528 or thesecond scroll 530 may also be performed by the exhaust gas divertervalve 540. The exhaust gas diverter valve 540 pivots about the pivot pin544. As is best shown in FIG. 5B, an actuator 548 such as a motor or ahydraulic actuator may be coupled to the exhaust gas diverter valve 540.Other types of actuators include pneumatic actuator. The actuator 548moves the exhaust gas diverter valve to the desired position in responseto various inputs as will be described in more detail below. That is,there may be conditions where both scrolls may be fully opened, or oneor the other scroll may be opened, at least partially. The opening andclosing of the valve may be used to control the pressure in the tunedpipe. Further, one scroll may be partially closed using the exhaust gasdiverter valve 540 while one scroll may be fully open as indicated bythe dotted lines. That is, in FIG. 5E the scroll 530 is completelyclosed by the edge 541 of the exhaust gas diverter valve 540 beingreceived within the valve seat 542B. In FIG. 5F the exhaust gas divertervalve 540 is in a middle or neutral position in which the first scroll528 and the second scroll 530 are fully opened. That is, the valve is ina fully opened position and is coincident to or parallel with theseparation wall 532. In FIG. 5G the edge 541 of the exhaust gas divertervalve 540 is received within and rests against the valve seat 542A tofully close the first scroll 528.

Referring now to FIGS. 5H and 5I, a butterfly type valve 550 may be usedin place of the diverter valve 540. The butterfly valve 550 pivots aboutpivot pin 544. The edge 552 of the valve 550 rests against the valveseat 556 in a closed position (FIG. 5I). The closure may result in aseal or a near closure if a protrusion 553A is on the edge 552 of valveor bump 553B on the seat 556. A dotted protrusion 553B is shown on theedges 552 and valve seat 556. The valve 550 may be in communication withan actuator and motor (or hydraulic actuator or a pneumatic actuator) tomove the valve 550 into the desired position. In this manner the valve550 is more balanced with respect to exhaust gas acting on the valveblade than the diverter valve 540.

Referring now to FIGS. 5J and 5K, alternate configuration for abutterfly type valve 560 may be used in place of the diverter valves 540and 550. The butterfly valve 560 is disposed within one of the scrolls.In this example scroll 530 has the first butterfly type valve 560. Thebutterfly valve 560 pivots about pivot pin 564. The edge 562 of thevalve 560 rests against the valve seat 566 in a closed position (FIG.5J). The valve 560 may be in communication with an actuator and motor(or hydraulic actuator or a pneumatic actuator) to move the valve 560into the desired position. In this manner, the valve 560 is morebalanced with respect to exhaust gas acting on the valve blade than thediverter valve 540.

In any of the examples in FIGS. 5A-5K, the valve 550 may also be madeoval. The closed position may be less than 90 degrees. The closure maynot be air tight intentionally. In addition, any of FIGS. 5A-5K may havethe protrusions 553A and/or 553B.

Referring now to FIGS. 6A-6F, an exhaust gas bypass valve 138 is setforth. By way of example, for a turbocharged engine the exhaust gasbypass valve 138 may be implemented in a wastegate or diverter valve.Some implementations do not have a turbocharger but an exhaust bypassvalve or wastegate is used to direct axhaust gasses from the tuned pipe.The exhaust gas bypass valve 138 may be configured in the bypass pipe136 that connects the exhaust gas from the exhaust manifold 45 and thetuned pipe 47 to an exhaust pipe 142 coupled to the outlet of theturbine portion of the turbocharger 140. Of course, as detailed below,the exhaust gas bypass valve 138 may be used in various positions withinthe exhaust assembly 44.

The exhaust gas bypass valve 138 has an exhaust gas bypass valve housing610. The exhaust gas bypass valve housing 610 may have a first flange612A and a second flange 612B. The flanges 612A, 612B are used forcoupling the exhaust gas bypass valve to the respective portions of thebypass pipe 136A, 136B. Of course, direct welding to the tuned pipe orbypass piping may be performed. The housing 610 has an outer wall 611that is generally cylindrical in shape and has a longitudinal axis 613which also corresponds to the general direction of flow through theexhaust gas bypass valve housing 610. The outer wall 611 has a thicknessT1.

The housing 610 includes a valve plate or valve member 614 that rotatesabout a rotation axis 616. The rotation axis 616 coincides with an axle618 that is coupled to the housing 610 so that the valve member 614rotates thereabout in a direction illustrated by the arrow 620. Thevalve member 614 is balanced to minimize the operating torque requiredto open/close the valve member 614. The butterfly arrangement hasexhaust gas working on both sides of the valve member 614, whicheffectively causes the forces to counteract and ‘cancel’ each other thatresults in a significantly reduced operating torque. Consequently, thevalve member 614 may be sized as wastegate as big as necessary withoutsignificantly increasing the operating torque to actuate it.Advantageously a smaller (and likely less expensive) actuator may beutilized.

The housing 610 may include a first valve seat 622 and a second valveseat 624. The seats 622 and 624 are integrally formed with the housing.As is illustrated, the valve seats 622 and 624 are thicker portions ofthe housing. The valve seats 622, 624 may have a thickness T2 greaterthan T1. Of course, casting thicknesses may change such as by providingpockets of reduced thickness for weight saving purposes. The valvesseats 622, 624 are circumferential about or within the housing 610.However, each of the valve seats 622 and 624 extends about half wayaround the interior of the housing to accommodate the axle 618.

The valve seats 622, 624 have opposing surfaces 626, 628 that have aplanar surface that are parallel to each other. The surfaces 626, 628contact opposite sides of the valve member 614 in the closed position.This allows the valve member 614 to rest against each valve seat 622,624 to provide a seal in the closed position. The exhaust gas bypassvalve 138 and the valve member 614 therein move in response to movementof an actuator 630. The actuator 630 rotates the valve member 614 aboutthe axis 616 to provide the valve member 614 in an open and a closedposition. Of course, various positions between open and closed areavailable by positioning the actuator 630. As will be further describedbelow, the actuator 630 may actuate the valve member 614, exhaust gasdiverter valve 540 and valves 550, 560 as described above. As mentionabove the surface area of the valve member 614 is the same above andbelow the axis 616 so that the operating toque is minimized due to theexhaust gas load being distributed evenly on both sides of the axis 616.

The effective cross-sectional area of opening, passage or port P1available to the exhaust gasses flowing through the interior of theexhaust gas bypass valve is limited by the distance T2 and the valvemember 614 and axle 618. After experimentation, it was found that theeffective cross-sectional area of the exhaust gas bypass valve 138 maybe formed as a function of an exducer of the turbine wheel 520 as isdescribed in greater detail below.

To vary the effective area, the valve member 614 of the exhaust gasbypass valve 138 has different angles α₁-α₄ illustrated in FIGS. 6B to6E respectively. The angles α₁-α₄ progressively increase. The angularopening corresponds directly with the effective area of the exhaust gasbypass valve 138. The angular opening of the exhaust gas bypass valve138 may be controlled in various ways or in response to variousconditions. Although specific angles are illustrated, the exhaust gasbypass valve 138 is infinitely variable between the fully closedposition of FIG. 6A and the fully open position of FIG. 6E.

Referring now to FIG. 6G, and end view of the exhaust gas bypass valve138 is illustrated in the open position corresponding to FIG. 6E.

Referring now to FIG. 6H, the exhaust gas bypass valve 138 may be incommunication with an electrical motor 640. The electrical motor 640 hasa position sensor 642 that provides feedback to a controller 644. Thecontroller 644 is coupled to a plurality of sensors 646. The sensorsprovide feedback to the controller 644 to control the position of thevalve 614 of the exhaust gas bypass valve 138. The sensors 646 mayinclude a boost pressure sensor, tuned pipe pressure sensor, exhaustmanifold pressure sensor and a barometric pressure sensor. Other typesof sensors that may be used for controlling the motor may includevarious types of temperature and pressure sensors for differentlocations within the vehicle.

Referring now to FIG. 6I, the turbine portion 510 is shown in relationto an exhaust gas bypass valve 138. In this example, a dual actuationsystem 650 is used to simultaneously move the diverter valves 540, 550and 560 illustrated above. The diverter valve 540 moves about the pivotpin 544. The exhaust gas bypass valve 138 opens and closes as describedabove. In this example, a rotating member 652 is coupled to a firstactuator arm 654 and a second actuator arm 656. As the rotating member652 moves under the control of a motor 658, the first actuator arm 654and the second actuator arm 656 move. According to that described below.Each actuator arm 654 and 656 may have a respective compensator 660,662. Although the type of movement described by the rotating member isrotating, other types of movement for the actuator arms may beimplemented. A compensator 660, 662 may thus be implemented in aplurality of different ways. The compensator 660, 662 may be used tocompensate for the type of movement as described below.

In this example, when the rotating member 652 is in a starting or homeposition, the exhaust gas bypass valve is closed and one scroll in theturbine is closed. As the dual actuation system 650 progresses theturbocharger scroll is opened and the diverter valve is positioned in acenter position so that both scrolls are open. As the dual actuationsystem 650 progresses to the end of travel the exhaust gas bypass valvestarts to open until it is fully open at the end of the actuator'stravel. The exhaust gas bypass valve 138 does not start to open untilthe diverter valve is in the neutral position and both scrolls are open.Once both scrolls are opened further actuator movement results in nomovement of the diverter valve in the turbo. The compensator 660, 662may be slots or springs that allow the exhaust gas bypass valve tocontinue to move. The compensators may also be a stop on the divertervalve so that when a diverter valve hits the center position the stopmay prevent the adjacent scroll from being closed. A compression springor other type of compensator may be used so that when the stop is hit,the actuator rod allows the compensator 662 to compress, thus stillallowing the actuator to turn the exhaust gas bypass valve 138. Ofcourse, various types of mechanisms for the dual actuation system 650may be implemented.

The wastegate may have a housing that is attached to a bracket forsupporting the wastegate actuator. The spring maintains the actuator inan open position should there be a mechanical or electrical fault.

Referring now to FIG. 6J, the wastegate housing 610 is illustrated infurther detail. The wastegate housing 610 has the valve member 614rotatably coupled thereto as described above. The valve member 614 has avalve stem 617 on which the valve member 614 rotates. The wastegatehousing 610 has a bracket 672 that has a first arm 672A, a second arm672B and a cross member 672C. The first arm 672A is coupled to thewastegate 610 at a first location spaced apart from a second location atwhich the arm 672B is coupled to the wastegate housing 610. Bosses 674A,674B may be integrally formed with the wastegate housing 610 or may beused to receive fasteners (not shown) that couple the respective arm672A, 674B to the bosses 674A, 674B. Bosses 674A, 674B may be integrallyformed with the wastegate housing 610 and are used to receive fasteners675 that couple the respective arm 672A, 674B to the bosses 674A, 674B.In the present example, the plane of the cross member 672C of thebracket 672 is perpendicular or normal to the axis formed by the valvestem 670.

A spring 676, as described above, may be used to maintain the actuatorin a particular position, such as an open position or a closed position,during operation. As the valve member 614 rotates, exhaust gases fromthe tuned pipe are communicated to bypass the turbocharger.

A drive housing 664 is coupled to the cross member 672C. The drivehousing 664 has a motor 666 with a motor shaft 666A as is bestillustrated in FIG. 6K. The motor shaft 666A is coupled to a connectionmechanism 667 that ultimately is coupled to a driveshaft 668. Theconnection mechanism 667 may comprise various types of gears such asspur gears or worm gears. The connection mechanism 667 may also be abelt or a chain drive. As the motor 666 rotates the motor shaft 666A,the connection mechanism 667 translates the motion and rotates thedriveshaft 668. The driveshaft 668 is coupled to the valve stem 670through a coupler 669. The coupler 669 allows the driveshaft 668 todirectly move the valve stem 670. A front view of the valve stem 670coupled to the coupler 669 and the valve member 614 is illustrated inFIG. 6L. In the example illustrated in FIG. 6J, the coupler 669 isdisposed between the wastegate housing 610 and the cross member 672C.Although not illustrated, the housing 674 may have a power connector 665for powering the motor 666.

Referring now to FIGS. 6J and 6M, the coupler 669 may comprise a firstlever arm 680A that has an opening 680 c therethrough. The coupler 669may also include a second lever arm 680B that has an opening 680 dtherethrough. The lever arm 680A is fixedly coupled to the driveshaft668. The lever arm 680B is fixed coupled to the valve stem 670. Afastener such as a bolt 682A couples the lever arm 680B to the lever arm680A with the use of a nut 682B. Of course, other fasteners, such asrivet, screw, clip or pin, may be used to couple the lever armstogether. When the lever arms 680A and 680B are coupled together, thelongitudinal axes of the driveshaft 668 and the valve stem 670 arecoaxial. The movement of the lever arms 680A and 680B cause the valvemember 614 to rotate into the desired position to allow exhaust gases tobe communicated from the pipe. In particular, exhaust gases arecommunicated from the center portion of the tuned pipe. In otherexamples, exhaust gases may be communicated in different ways anddifferent positions relative to the engine including other positions ofthe tuned pipe.

Referring now to FIG. 6N, an alternate location for the drive housing664 may be coupled to a bracket 680. The bracket 680, in this example,is coupled to the compressor housing or compressor portions 512 of theturbocharger 140. As was described above, a turbine portion 510, whichmay be referred to as the turbine housing, is coupled to the compressorportion 512. The driveshaft 668 is illustrated coupled to a flexibledrive or flexible coupling 681. The flexible coupling 681 is also shownin more detail in FIG. 6O. The flexible coupling 681 has an outer sheath681A and a rotating member 681B that rotates with the driveshaft 668. Afastener 682A couples the driveshaft 668A to the rotating member 681B. Afastener 682B couples the rotating member 681B to the valve stem 670.Various types of fasteners may be used including but not limited toclips, rivets, screws and combinations thereof. The advantage of using aflexible coupling 681 is the location may be varied. The bracket 680 mayalso be used in other locations of the vehicle, such as a frame or thelike (not shown). This allows the bracket 680 and the drive housing 664to be mounted in a number of different locations of the vehicle.

Referring now to FIG. 6P, another position for a bracket 684 isintegrally formed with the compressor housing 612. During the formationor molding of the compressor housing 512, the bracket 684 may beintegrally formed therein. The reduces the overall part count of thesystem. The housing 664 is coupled to the bracket that is integrallyformed with the compressor housing 512 using fasteners 685 or the like.In this example, the exhaust bypass pipe 686 is also illustrated. Theexhaust bypass pipe 686 was eliminated for clarity in FIG. 6N. Theexhaust bypass pipe communicates exhaust gases from the tuned pipe 47and in particular the center portion 47B of the tuned pipe 47 to thesilencer 710.

Referring now to FIG. 6Q, a clamp 688 may be used to couple thewastegate housing 610 to the center portion 47B of the tuned pipe 47.The clamp 688 is coupled to a flange 689 that may be integrally formedwith the center portion 47B of the tuned pipe 47. A flange 690 formed onthe wastegate housing 610 may also be received in the clamp. A fastener692 may be used to secure the clamp 688 to the flanges 689 and 690. Inparticular, a pair of grooves 694 on the internal diameter of the clamp688 may receive the flanges 689, 690 for securing therein. The fasteners692 may be tightened to couple the wastegate housing 610 to the flange689.

Referring now to FIGS. 7A-7C, the position of the exhaust gas bypassvalve 138 relative to the turbocharger and the silencer of the vehiclemay be changed. Although the turbocharger 140 is illustrated, thefollowing descriptions may be applied to normally aspirated(non-turbocharged) engines.

Referring now specifically to FIG. 7A, the engine assembly 40 has theexhaust manifold 45 as illustrated above. The tuned pipe 47 communicatesexhaust gases from the exhaust manifold 45 to the stinger 134. Thestinger 134 is in communication with the turbocharger 140, and inparticular the turbine inlet 524 of the turbine portion 510. In anon-turbocharged engine the stinger 134 may be communicated to thesilencer 710. Exhaust gases pass through the turbine portion 510 andexit through outlet 526 at a lower total energy. In this example thebypass pipe 136A extends from the tuned pipe 47 to the exhaust pipe 142.In particular, the bypass pipe is illustrated in communication with thecenter portion 47B of the tuned pipe 47. The exhaust gas bypass valve138 is positioned within the bypass pipe 136A. The outlet of the bypasspipe 136 communicates with the exhaust pipe 142 before a silencer 710.The silencer 710 has an exhaust outlet 143.

An inlet source 712 communicates air to be compressed to the compressorportion 512 of the turbocharger 140. The compressed air is ultimatelyprovided to the engine assembly 40.

As shown is dotted lines, the bypass pipe 136A may also be coupled tothe exhaust manifold 45, the diverging portion 47A of the tuned pipe 47,the converging portion 47C of the tuned pipe or the stinger 134.

Should the turbocharger 140 be removed, the exhaust pipe 142 isconnected directly to the stinger 134. The inlet source 712 is notrequired.

Referring now to FIG. 7B, the silencer 710 may include a plurality ofchambers 720A-720C. In the example set forth in FIG. 7B, all of the samereference numerals are used. However, in this example, the bypass pipe136B communicates exhaust gases around the turbocharger 140 bycommunicating exhaust gases from the center portion 47B of the tunedpipe 47 through the exhaust gas bypass valve 138 to a first chamber 720Aof the silencer 710. It should be noted that the outlet of the bypasspipe 136B is in the same chamber as the exhaust gases entering from theexhaust pipe 142.

As shown in dotted lines, the bypass pipe 136B may also be coupled tothe exhaust manifold 45, the diverging portion 47A of the tuned pipe 47,the converging portion 47C of the tuned pipe or the stinger 134.

As in FIG. 7A, should the turbocharger 140 be removed, the exhaust pipe142 is connected directly to the stinger 134. The inlet source 712 isnot required.

Referring now to FIG. 7C, the bypass pipe 136C communicates fluidicallyfrom the tuned pipe 47 to a first chamber 720A of the silencer 710. Inthis example, the first chamber 720A is different than the chamber thatthe exhaust pipe 142 from the turbocharger entering the silencer 710.That is, the exhaust pipe 142 communicates with a third chamber 720C ofthe silencer while the bypass pipe 136C communicates with a firstchamber 720A of the silencer 710. Of course, multiple chambers may beprovided within the silencer 710. The example set forth in FIG. 7Cillustrates that a bypass pipe 136C may communicate exhaust gases to adifferent chamber than the exhaust pipe 142.

As in the above, should the turbocharger 140 be removed, the exhaustpipe 142 is connected directly to the stinger 134. The inlet source 712is not required.

Referring now to FIG. 7D, engine assembly 40 is illustrated having afourth example of an exhaust gas configuration. In this case, bypasspipe 136D does not connect to the exhaust pipe 142. The outlet of theexhaust gas bypass valve 138 connects to the atmosphere directly orthrough a supplemental silencer 730 then to the atmosphere. Theconfiguration of FIG. 7D is suitable if packaging becomes an issue.

As shown is dotted lines, the bypass pipes 136C, 136D in FIGS. 7C and 7Dmay also be coupled to the exhaust manifold 45, the diverging portion47A of the tuned pipe 47, the converging portion 47C of the tuned pipeor the stinger 134.

As in the above, should the turbocharger 140 be removed, the exhaustpipe 142 is connected directly to the stinger 134. The inlet source 712is not required.

Referring now to FIG. 7E, a two-stroke engine system is set forth. Inthe present system an engine assembly 40 is coupled to an exhaustmanifold 45. The exhaust manifold 45 is in communication with the tunedpipe 47. The tuned pipe 47 has a divergent portion 47A, a center portion47B and a convergent portion 47C. The divergent portion 47A widens thetuned pipe 47 to the center portion 47B. The center portion 47B may be arelatively straight portion or a portion that has a generally constantcross-sectional area. The convergent portion 47C reduces the diameter ofthe center portion 47B to a diameter that is in communication with thestinger 134. Exhaust gases from the exhaust manifold 45 travel throughthe divergent portion 47A and the center portion 47B and the convergentportion 47C in a “tuned” manner. That is, the portions 47A-47C are tunedfor the particular design of the engine to provide a certain amount ofback pressure. Thus, a certain amount of power and stability is designedinto the engine assembly. The exhaust gases travel from the stinger 134to a silencer 710. As described above a turbocharger 140 may be used torecover some of the energy in the exhaust gases. The tuned pipe 47 has atuned pipe pressure sensor 734 that is coupled to the tuned pipe 47 tosense the amount of exhaust gas pressure within the tuned pipe 47. Thetuned pipe pressure sensor 734 generates a signal corresponding to theexhaust gas pressure within the tuned pipe 47.

An exhaust gas bypass valve 740 in this example is coupled directly tothe exhaust manifold 45. The exhaust gas bypass valve 740 provides abypass path through the bypass pipe 136 which may enter either thesilencer 710 or communicate directly to atmosphere through asupplemental silencer 730. Of course, the bypass pipe 136 may beconfigured as set forth above in the pipe between the turbocharger 140and the silencer 710. The exhaust gas bypass valve 740 may beelectrically coupled to a controller as will be described further below.Based upon various engine system sensor signals, exhaust gas bypassvalve 740 may be selectively opened to provide an increase in power andor stability for the engine assembly 40. The exhaust gas bypass valve740 changes the pressure within the tuned pipe 47 so the airflow throughthe engine is increased or decreased, by changing the differentialpressure across the engine. A change in the airflow may be perceived asan increase in power, engine stability or improved combustion stabilityor a combination thereof.

Referring now to FIG. 7F, the exhaust gas bypass valve 740′ may bedisposed on the center portion 47B of the tuned pipe 47. However, theexhaust gas bypass valve 740′ may also be located on the divergentportion 47A or the convergent portion 47C as illustrated in dottedlines. In the example set forth in FIG. 7F the exhaust gas bypass valve740′ is mounted directly to the outer wall 741 of the center portion 47Bof the tuned pipe 47. The exhaust gas bypass valve 740′ may also becoupled to the stinger 134 also as illustrated in dotted lines.

Referring now to FIG. 7G, the exhaust gas bypass valve 740″ may bepositioned away from the outer wall 741 of the tuned pipe 47 by astandoff pipe 742. The standoff pipe 742 may be very short such as a fewinches. That is, the standoff pipe 742 may be less than six inches.Thus, the exhaust gas bypass valve 740″ may be positioned in a desirablelocation by the standoff pipe 742 due to various considerations such aspackaging.

In this example standoff pipe 742 and hence the exhaust gas bypass valve740″ is coupled to the center portion 47B of the tuned pipe 47. However,as illustrated in dotted lines, the standoff pipe 742 may be may becoupled to the exhaust manifold 45, the diverging portion 47A, theconverging portion 47C or the stinger 134.

The valve 740′″ may also be located within the center portion 47B of thetuned pipe 47. The valve 740′″ may also be located within the divergentportion 47A or the convergent portion 47C or in the exhaust manifold asillustrated in dotted lines.

Referring now to FIG. 7H, a control valve 740′″ may be disposed withinthe stinger 134. The valve 740″ may not communicate bypass exhaustgasses out of the exhaust stream but the control valve 740′″ may beconfigured in a similar manner as the exhaust gas bypass valvesdescribed above with controlled flow therethrough. Valve 740″ may bepartially opened in the most closed position to allow some exhaustgasses to flow there through. Although the valve 740′″ may be used in aturbocharged application, a normally aspirated engine application may besuitable as well. The valve 740′″ may open in response to variousconditions so that the power output of the engine may be adjusteddepending on such inputs as throttle, load engine speed, tuned pipepressure and temperature, exhaust pressure and temperature. Otherlocation of the control valve 740′″ are also illustrated in thediverging portion 47A of the tuned pipe 47, the middle portion 47B andthe converging portion 47C of the tuned pipe.

The exhaust gas bypass valves 740, 740′, 740″ and 740′″ may have varioustypes of configurations. In one example the exhaust gas bypass valve740-740′″ may be configured as an exhaust gas bypass valve similar tothat set forth above and used to bypass the turbocharger 140. Thestructural configuration of the valves 740-740′″ may include but are notlimited to a butterfly valve, a slide valve, a poppet valve, a ballvalve or another type of valve.

Referring now to FIG. 7I, the exhaust bypass valve 740 illustrated abovemay be implemented within a first chamber 720A of the silencer 710. Inthis example, the tuned pipe 47 communicates exhaust gasses to thesilencer 710. The tuned pipe 47 may communicate exhaust gasses from afirst portion 747A, a center portion 747B, or a third portion 747C.These are illustrated in the above examples. The exhaust bypass valve740′″ is disposed within one of the chambers 720A-720C. In this example,the exhaust bypass valve 740′″ is disposed within the first chamber720A. In this example, the turbocharger140 communicates exhaust gassesto the silencer through the pipe 142. In this example, theturbocharger140 is coupled to the pipe 142 which is in communicationwith the first chamber 720A. However, any one of the chambers 720A-720Cmay receive exhaust gasses from the turbocharger 140 through the pipe142.

Referring now to FIG. 7J, the chamber 720A illustrated in FIG. 1 isdivided into a first chamber portion 720A′ and a second chamber portion720A″ which are separated by a wall 746. Exhaust gasses are communicatedbetween the first chamber portion 720A′ and the second chamber portion720A″ through the exhaust bypass valve 740 ^(IV).

The valve 740′″ and 740 ^(IV) are provided to control the amount ofpressure in various tuning characteristics of the tuned pipe 47. In FIG.7J, the turbocharger140 may be in communication with any one of thechambers 720A″, chamber 720B, and chamber 720C.

Any of the chambers 720A-C may be divided into two chambers.

Referring now to FIG. 7K, the supplemental silencer 730 and the silencer710 may be disposed as a single unit. The supplemental silencer 730 maybe disposed in a common housing but maintain separate flow paths fromthe valve 138 and the turbocharger 140. The silencer 710 and thesupplemental silencer 730 may have a common wall 724 therebetween. Thecommon wall reduces manufacturing costs and vehicle weight by reducingthe amount of wall material.

Referring now to FIG. 7L, a simplified version of FIGS. 7A through 7K isset forth. In FIGS. 7L through 7N, components such as the engineassembly and all of the piping is eliminated for simplicity purposes. Ofcourse, although the turbocharger 140 is illustrated, the turbocharger140 in FIGS. 7L through 7N correspond to the turbine portion of theturbocharger 140.

Referring now specifically to FIG. 7L, the turbocharger 140 receivesexhaust gases from the stinger and tuned pipe which originated from theengine. The wastegate 740 receives bypass exhaust gases from the tunedpipe. The muffler 750 receives exhaust gases from the pipe 142 at port750A and exhaust gases from pipes 136D at port 750B. The muffler 750 maybe one singular muffler or may include a separate wall 752 to keep theexhaust gases separate. That is, wall 752 is an optional component. Apipe 754 is coupled to both sides of the wall 752 and receive exhaustgases from each side of the muffler 750. That is, exhaust gases thatoriginated at port 750A and 750B are ultimately combined in the pipe754.

Referring now to FIG. 7M, pipe 142 from turbocharger 140 and pipe 136Dfrom the wastegate 740 are joined together at a joint 756. The joint isa Y-joint that comes together before the silencer 710. Ultimately, thesilencer 710 so that the silencer 3 710 includes one inlet pipe 758 andone outlet pipe 760.

Referring now FIG. 7N, the pipe 758 is coupled to a flange 762 prior toentering the silencer 710. In a practical example, the flange 762 andthe joint 756 may all be formed as one component. The flange 762 may beused to increase the manufacturability of the configuration.

Referring now to FIG. 7O, the engine assembly 40, the tuned pipe 47 andthe turbocharger 140 are all illustrated. The wastegate or exhaustbypass valve 740 is illustrated coupled to the center section 47B. Inthis example, the effective area of cross-sectional flow of thewastegate or exhaust bypass valve 740 is greater than the cross-sectionflow area of the stinger 134. Correspondingly, the cross-sectional flowarea of the pipes 136D and 136 also have a cross-sectional flow areaabout or greater than that of the cross-sectional flow area of thewastegate or exhaust bypass valve 740.

Referring now to FIG. 8A, schematic view of an engine air system that aboost box 810 is illustrated. The boost box 810 has a one-way valve 812coupled therein. The valve 812 may be an active valve such as a motorcontrolled valve or a passive valve such as a reed valve. When a lowerpressure is present in the boost box 810 than the ambient pressureoutside the boost box 810, the valve 812 opens and allows air to bypassthe compressor portion 512 of the turbocharger 140. That is, a bypasspath is established through the boost box from the valve 812 throughboost box 810 to the engine. That is, the air through the valve 812bypasses the compressor portion 512 of the turbocharger 140 and the airin boost box 810 is directed to the air intake or throttle body of theengine assembly 40.

The one-way valve 812 may be a reed valve as illustrated in furtherdetail in FIG. 8F. By using a one-way valve 812, engine response isimproved to activate turbocharger 140 sooner. When the engine responseis improved the turbocharger lag is reduced by allowing the engine togenerate exhaust mass flow quicker, in turn forcing the turbine wheelspeed to accelerate quicker. When the compressor portion 512 of theturbocharger 140 builds positive pressure the one-way valve 812 closes.When implemented, a decrease in the amplitude and duration of the vacuumpresent in the boost box 810 was achieved. In response, the engine speedincreased sooner, and the compressor built positive pressure sooner.

Referring now to FIGS. 8A-8F, the boost box 810 has the one-way valve812 as described above. The one-way valve 812 allows air into the boostbox 810 while preventing air from leaving the boost box 810. The boostbox 810 also includes a compressor outlet 814. The compressor outlet 814receives pressurized air from the compressor portion 512 of theturbocharger 140. However, due to turbocharger lag the compressor takessome time to accelerate and provide positive pressure to the boost box810 particularly when wide open throttle is demanded suddenly from aclosed or highly throttled position.

The boost box 810 also includes a pair of intake manifold pipes 816 thatcouple to the throttle body 90 of the engine assembly 40.

A portion of a fuel rail 820 is also illustrated. The fuel rail 820 maybe coupled to fuel injectors 822 that inject fuel into the boost box 810or throttle body 90. The fuel rail 820 and fuel injectors 822 may alsobe coupled directly to the throttle body 90.

A pressure sensor 824 may also be coupled to the boost box 810 togenerate an electrical signal corresponding to the amount of pressure inthe boost box 810, which also corresponds to the boost provided from thecompressor portion 512 of the turbocharger 140. The boost box pressuresensor signal takes into account the boost pressure and the barometricpressure. That is the boost box pressure sensor signal is a function ofboth the boost pressure and the barometric pressure.

Referring now to FIG. 8F, the one-way valve 812 is illustrated infurther detail. The one-way valve 812 may include a plurality of ports830 that receive air from outside of the boost box 810 and allow air toflow into the boost box 810. That is, when a lower pressure is developedwithin the boost box 810 such as under high acceleration or load, theturbocharger 140 is not able to provide instantaneous boost and thus airto the engine is provided through the one-way valve 812 to reduce oreliminate any negative pressure, relative to ambient pressure outsidethe boost box, within the boost box 810. When compressor portion 512 ofthe turbocharger 140 has reached operating speed and is pressurizing theboost box 810, the pressure in the boost box 810 increases and theone-way valve 812 closed. That is, the ports 830 all close when pressurewithin the boost box 810 is higher than the ambient pressure outside theboost box.

Referring now to FIG. 8G, the boost box 810 is illustrated within anengine compartment 832. The engine compartment 832 roughly illustratesthe engine assembly 40 and the turbocharger 140. In this example theone-way valve 812 is illustrated rearward relative to the front of thevehicle. The position of the one-way valve 812 allows cooler air to bedrawn into the boost box 810.

Referring now to FIG. 8H, the one-way valve 812 may be coupled to a duct840. The duct 840 allows cooler air to be drawn into the boost box 810from a remote location. In this example, an upper plenum 842 is coupledto the duct 840. The upper plenum may pass the air through a filter 862,such as a screen or fine mesh, prior to being drawn into the boost box810. The filter 862 may filter large particles and prevent damage to theboost box 810 and the one-way valve 812. The upper plenum receives airfrom a vent 846. A filter 862′ may be located at the vent 846 or betweenthe vent 846 and upper plenum 842. Of course, in one system one filter862 or the other filter 862′ may be provided.

The vent 846 may be located in various places on the vehicle. Forexample, the vent 846 may draw air externally though the hood of thevehicle, the console of the vehicle or from a location under the hoodthat has clean and cool air.

Referring now to FIG. 8I, a channel 850 may be formed in the fuel tank852. That is, the channel 850 may act as the duct 840 illustrated abovein FIG. 8H. The channel 850 may be integrally formed into the outerwalls 854 of the fuel tank. The boost box 810 may be attached to thefuel tank 852 so that the air drawn into the boost box 810 is receivedthrough the channel 850. A seal 856 may be used between the boost boxand the fuel tank 852 so that the air is completely drawn through thechannel 850. Various types of seals may be used. Rubber, foam,thermoplastics are some examples. The seal 856 may be a gasket. A duct860 may be coupled between the fuel tank 852 and the boost box 810 toreceive air from a remote location such as the vent 846 illustrated inFIG. 8H or another location within the engine compartment 832 of thevehicle. Of course, the duct 860 may draw air from other portions of thevehicle or outside the vehicle. A filter or screen 862 may be used toprevent debris from entering the channel 850.

Referring now to FIG. 9A, a block diagrammatic view of a control systemfor a two-stroke turbocharged engine is set forth. In this example acontroller 910 is in communication with a plurality of sensors. Thesensors include but are not limited to a boost pressure sensor 912, anengine speed sensor 914, an atmospheric (altitude or barometric)pressure sensor 916, a throttle position sensor, tuned pipe pressuresensor 734, an exhaust valve position sensor 937 and an exhaust manifoldpressure sensor. Each sensor generates an electrical signal thatcorresponds to the sensed condition. By way of example, the boostpressure sensor 912 generates a boost pressure sensor signalcorresponding to an amount of boost pressure. The engine speed sensor914 generates an engine speed signal corresponding to a rotational speedof the crankshaft of the engine and the atmospheric or barometricpressure sensor 916 generates a barometric pressure signal correspondingto the atmospheric ambient pressure.

The tuned pipe pressure sensor 734 may also be in communication with thecontroller 910. The tuned pipe pressure sensor 734 generates a tunedpipe pressure signal corresponding to the exhaust pressure within thetuned pipe 47 as described above. The exhaust valve position sensor 937generates an exhaust valve position signal corresponding to the positionof the exhaust valve. The exhaust manifold pressure sensor 939 generatesa signal corresponding to the pressure in the exhaust manifold. Avehicle speed sensor 939A generates a speed signal corresponding to thespeed of the vehicle. An exhaust gas temperature sensor 939B generatesan exhaust gas temperature signal, an exhaust valve position sensor 939Cgenerates an exhaust valve position signal, and a post compressortemperature sensor 939D generates a temperature signal of thetemperature of the exhaust after the compressor.

The controller 910 is used to control an actuator 920 which may becomprised of an exhaust gas bypass valve actuator 922 and exhaust gasdiverter valve actuator 924. An example of the actuator is illustratedin FIG. 6I above. Of course, as mentioned above, the actuators may beone single actuator. The actuator 922 is in communication with theexhaust gas bypass valve 138. The actuator 924 is in communication withthe exhaust gas diverter valve 540. The controller 910 ultimately may beused to determine an absolute pressure or a desired boost pressure.

A boost error determination module 930 is used to determine a boosterror. The boost error is determined from the boost pressure sensor 912in comparison with the desired boost pressure from the boost pressuredetermination module 932. The boost pressure error in the boost pressuredetermination module 930 is used to change an update rate fordetermining the boost pressure for the system. That is, the boost errordetermination is determined at a first predetermined interval and may bechanged as the boost error changes. That is, the system may ultimatelybe used to determine an update rate at a faster rate and, as the boostpressure error is lower, the boost pressure determination may determinethe desired boost pressures at a lower or slower rate. This will bedescribed in further detail below. This is in contrast to typicalsystems which operate a PID control system at a constant update rate.Ultimately, the determined update rate is used to control the exhaustgas bypass valve using an exhaust gas bypass valve position module 934which ultimately controls the actuator 920 or actuator 922 depending ifthere is a dedicated actuator for the exhaust gas bypass valve 138. Bydetermining the boost target in the boost pressure determination module932, the update rate may be changed depending on the amount of boosterror. By slowing the calculations, and subsequent system response,during the approach of the target boost value, overshoot is controlledand may be reduced. Also, the update rate may be increased to improvesystem response when large boost errors are observed.

The controller 910 may be coupled to a detonation sensor 935. Thedetonation sensor 935 detects detonation in the engine. Detonation maybe referred to as knock. The detonation sensor 935 may detect an audiblesignal.

The controller 910 may also include an absolute pressure module 936 thatkeeps the engine output constant at varying elevations. That is, bycomparing the altitude or barometric pressure from the atmosphericpressure sensor 916, the boost pressure may be increased as theelevation of the vehicle increases, as well as to compensate forincreased intake air charge temperature due to increased boost pressureto maintain constant engine power output. This is due to the barometricpressure reducing as the altitude increases. Details of this will be setforth below.

The controller 910 may also include a second exhaust gas bypass valveposition control module 938. The exhaust gas bypass valve positioncontrol module 938 is used to control the exhaust gas bypass valve andposition the actuator 926 which may include a motor or one of the othertypes of valve described above. The exhaust gas bypass valve positioncontrol module 938 may be in communication with the sensors 912-918, 935and 734. The amount of pressure within the tuned pipe may affect thestability and power of the engine. Various combinations of the signalsmay be used to control the opening of the exhaust gas bypass valve740-740″. The exhaust gas bypass valves 740-740″ may, for example, becontrolled by feedback from the tuned pipe pressure sensor 734. Thetuned pipe pressure sensor signal may be windowed or averaged to obtainthe pressure in the tuned pipe as a result of the opening or closing ofthe exhaust gas bypass valve 740-740″. The tuned pipe pressure sensor734 may be used in combination with one or more of the other sensors912-918, 734 and others to control the opening and closing of theexhaust gas bypass valve 740-740″. The boost pressure or average boostpressure from the boost pressure sensor 912 may also be used to controlthe exhaust gas bypass valves 740-740″. The boost pressure determinationmodule 932 may provide input to the exhaust gas bypass valve positioncontrol module 938 to control the exhaust gas bypass valve based uponthe boost pressure from the boost pressure determination module 932 asdescribed above.

A map may also be used to control the specific position of the exhaustgas bypass valve 740-740″. For example, the engine speed signal, thethrottle position signal and/or the barometric pressure signal may allbe used together or alone to open or close the exhaust gas bypass valve740-740″ based on specific values stored within a pre-populated map.

Referring now to FIG. 9B, in step 940 the actual boost pressure ismeasured by the boost pressure sensor 912 as mentioned above. In step942 a boost pressure error is determined. Because this is an iterativeprocess, the boost error is determined by the difference between thetarget boost and the actual boost pressure. Once the process is cycledthrough once, a boost error will be provided to step 942.

Referring to step 944, the update interval is changed based upon theboost error determination in step 942. That is, the boost error is usedto determine the update rate of the exhaust gas bypass valve controlmethod. That is, the update rate corresponds to how fast the method ofdetermining error, then moving the exhaust gas bypass valve actuator,and determine timing of the next cycle is performed. As mentioned above,as the actual boost or measured boost pressure becomes closer to thetarget boost pressure the update rate is reduced in response to theobserved boost error.

In step 946 a desired absolute pressure is established. Step 946 may beestablished by the manufacturer during the vehicle development. Thedesired absolute pressure may be a design parameter. In step 948 thebarometric pressure of the vehicle is determined. The barometricpressure corresponds to the altitude of the vehicle. In step 950 arequired boost pressure to obtain the absolute pressure and overcomeadditional system losses due to elevation is determined. That is, thebarometric pressure is subtracted from the required absolute pressure todetermine the desired boost pressure. In step 952 the exhaust gas bypassvalve and/or the exhaust gas diverter valve for the twin scrollturbocharger is controlled to obtain the desired boost pressure. Becauseof the mechanical system the desired boost pressure is not obtainedinstantaneously and thus the process is an iterative process. That is,the required boost pressure from step 950 is fed back to step 942 inwhich the boost error is determined. Further, the after step 952 step940 is repeated. This process may be continually repeated during theoperation of the vehicle.

Referring now to FIG. 9C, a throttle position sensor 918 may provideinput to the controller 910. The throttle position sensor signal 954 isillustrated in FIG. 9C. The engine speed signal 960 is also illustrated.The signal 958 illustrates the position of the exhaust gas bypass valve.The signal 956 illustrates the amount of boost error.

Referring now to FIG. 9D, a plot of a calculation multiplier delayversus the absolute boost error pressure is set forth. As can be seen asthe boost error decreases the frequency of calculations decreases. Thatis, as the boost error increases the frequency of calculationsincreases.

Referring now to FIG. 9E, a plot of absolute manifold pressure versuselevation is set forth. The barometric pressure and the boost pressurechange to obtain the total engine power or target absolute pressure.That is, the absolute pressure is a design factor that is keptrelatively constant during the operation of the vehicle. As theelevation increases the amount of boost pressure also increases tocompensate for the lower barometric pressure at higher elevations aswell as increased intake air temperature.

Referring now to FIG. 9F, a method for operating the exhaust gas bypassvalve 740-740″ is set forth. In this example the various engine systemsensors are monitored in step 964. The engine sensors include but arenot limited to the boost sensor 912, the engine speed sensor 914, thealtitude/barometric pressure sensor 916, the throttle position sensor918 and the tuned pipe pressure sensor 734.

In step 966 the exhaust gas bypass valve 740-740″ is adjusted based uponthe sensed signals from the sensors. The adjustment of the opening instep 966 may be calibrated based upon the engine system sensors duringdevelopment of the engine. Depending upon the desired use, the load andother types of conditions, various engine system sensors change and thusthe amount of stability and power may also be changed by adjusting theopening of the exhaust gas bypass valve.

In step 968, the pressure within the tuned pipe is changed in responseto adjusting the opening of the exhaust gas bypass valve 740-740″. Inresponse to changing the pressure within the tuned pipe, the airflowthrough the engine is changed in step 969. When the airflow through theengine is changed the stability of the engine, the power output of theengine or the combustion stability or combinations thereof may also beimproved. It should be noted that the opening of the exhaust gas bypassvalve 740-740″ refers to the airflow though the exhaust gas bypass valve740-740″. Thus, the opening may be opened and closed in response to theengine system sensors.

Referring now to FIG. 9G, the exhaust gas bypass valve position controlmodule 934 is illustrated in further detail. As mentioned above, theexhaust gas bypass valve effective area may be varied depending onvarious operating conditions. The addition of a turbocharger to atwo-stroke engine adds the restriction of the turbine which causes theengine to respond slower than a naturally aspirated engine of similardisplacement. The loss of response caused from the turbine may be viewedby a vehicle operator as turbocharger lag.

The exhaust gas bypass valve position module 934 is illustrated havingvarious components used for controlling the exhaust gas bypass valve. Anidle determination module 970 is used to receive the engine speedsignal. The idle determination module may determine that the enginespeed is below a predetermined speed. A range of speeds may be used todetermine whether or not the engine is at idle. For example, a rangebetween about 1000 and 2000 rpms may allow the idle determination module970 to determine the engine is within or at an idle speed. Idle speedsvary depending on the engine configuration and various other designparameters. Once the engine is determined to be at idle the exhaust gasbypass valve effective area module 972 determines the desired effectiveexhaust gas bypass valve area for the exhaust gas bypass valve. Theexhaust gas bypass valve effective area module 972 determines theopening or effective area of the exhaust gas bypass valve for thedesired control parameter. For idle speed, a first effective exhaust gasbypass valve area may be controlled. That is, one effective exhaust gasbypass valve area may be used for idle speed determination. Once theexhaust gas bypass valve area is determined the exhaust gas bypass valveactuator 922 may be controlled to open the exhaust gas bypass valve afirst predetermined amount. The exhaust gas bypass valve for idle may beopened a small effective area. That is, the exhaust gas bypass valve maybe opened further than a fully closed position but less than a fullyopened position. For exhaust gas bypass valve such as those illustratedin FIG. 6 above about twenty degrees of opening may be commanded duringthe idling of the two-stroke engine. By opening the exhaust gas bypassvalve a predetermined amount some of the exhaust gases are bypassedaround both the turbine portion 510 of the turbocharger 140 and thestinger 134 at the end of the tuned pipe. The effective predeterminedarea may change depending on various sensors including but limited to inresponse to one or more of the engine speed from the engine speedsensor, throttle position from the throttle position sensor or adetonation from the detonation sensor.

The exhaust gas bypass valve position control module 934 may alsocontrol the exhaust gas bypass valve position during acceleration or toimprove engine stability. Acceleration of the engine may be determinedin various ways including monitoring the change in engine speed,monitoring the throttle position or monitoring the load on the engine.Of course, combinations of all three may be used to determine the engineis accelerating. When the engine is accelerating as determined in theacceleration determination module 974 the exhaust gas bypass valveeffective area module 972 may hold the exhaust gas bypass valve open apredetermined amount. The predetermined amount may be the same ordifferent than the predetermined amount used for the engine idle. Again,some of the exhaust gases are bypassed around the stinger 134 and theturbine portion 510 of the turbocharger 140. The determined exhaust gasbypass valve effective area is then commanded by the exhaust gas bypassvalve effective area module 972 to control the exhaust gas bypass valveactuator module 922. In a similar manner, the engine sensor may be usedto monitor engine stability. In response, the wastegate may open forvarious amounts of time to increase engine stability.

Referring now to FIG. 9H, a method for operating the exhaust gas bypassvalve in response to acceleration and idle is set forth. In step 980 theengine speed is determined. As mentioned above, the crankshaft speed maybe used to determine the speed of the engine. In step 982 is todetermine whether the engine is at idle. Determining the engine is atidle may be performed by comparing the engine speed to an engine speedthreshold or thresholds. When the engine speed is below the engine speedthreshold or between two different engine speed thresholds, the engineis at idle. When the engine is at idle, step 984 determines an effectivearea for the exhaust gas bypass valve and opens the exhaust gas bypassvalve accordingly. In step 986 some of the exhaust gases are bypassedaround the stinger 134 and the turbine portion 510 as described above.

When the engine is not at idle in step 982 and after step 986, step 988determines whether the engine is in an acceleration event. As mentionedabove, the acceleration event may be determined by engine speed alone,load alone or the throttle position or combinations of one or more ofthe three. When the engine is in an acceleration event step 990 holdsthe exhaust gas bypass valve to a predetermined amount to reduce thebackpressure. The predetermined amount may be the same predeterminedamount determined in step 984. The effective area may be controlled bythe valve in the exhaust gas bypass valve or another type of openingcontrol in a different type of exhaust gas bypass valve. In step 992some of the exhaust gases are bypassed around the stinger 134 andturbine portion 510.

Referring back to step 988, if the engine is not in an accelerationevent the engine operates in a normal manner. That is, in step 994 theboost pressure or exhaust backpressure is determined. In step 996 theexhaust gas bypass valve opening is adjusted based upon the boostpressure, the exhaust backpressure or both. After step 996 and step 992the process repeats itself in step 980.

Referring now to FIGS. 10A, 10B, 10C and 10D, the compressor wheel 519,the turbine wheel 520 and the shaft 521 are illustrated in furtherdetail. The compressor wheel 519 is used to compress fresh air intopressurized fresh air. The compressor wheel 519 includes an inducerdiameter 1010 and an exducer diameter 1012. The inducer diameter 1010 isthe narrow diameter of the compressor wheel. The exducer diameter 1012is the widest diameter of the compressor wheel 519.

The turbine wheel 520 includes an exducer diameter 1020 and an inducerdiameter 1022. The exducer diameter 1020 is the small diameter of theturbine wheel 520. The inducer diameter 1022 is the widest diameter ofthe turbine wheel 520. That is, the top of the blades 1024 have theexducer diameter 1020 and the lower portion of the blades 1024 have theinducer diameter 1022. The exducer diameter 1020 is smaller than theinducer diameter 1022. The area swept by the blades 1024 is bestillustrated in FIG. 10C which shows the exducer area 1030 and theinducer area 1032. The area of the port of the exhaust gas bypass valvewas described above relative to FIG. 6G. The port area is the amount ofarea available when the valve member 614 is fully open. By sizing thearea of the exhaust gas bypass valve port in a desirable way theoperation of the two-stroke engine performance is increased. As has beenexperimentally found, relating the exhaust gas bypass valve effectivearea (port area) to the area of the turbine wheel exducer isadvantageous. The exducer area 1030 may be determined by the geometricrelation π times half of the exducer diameter squared. By way of a firstexample, the port area for a two-stroke engine may be greater than aboutthirty-five percent of the exducer area. The port area of the exhaustgas bypass valve may be greater than about fifty percent of the exducerarea. In other examples the port area of the exhaust gas bypass valvemay be greater than about sixty percent of the exducer area. In anotherexample the port area of the exhaust gas bypass valve may be greaterthan about sixty-five percent of the exducer area. In yet anotherexample the port area of the exhaust gas bypass valve may be greaterthan about sixty-five percent and less than about ninety percent of theexducer area. In another example the port area of the exhaust gas bypassvalve may be greater than about sixty-five percent and less than abouteighty percent of the exducer area. In yet another example the port areaof the exhaust gas bypass valve may be greater than about seventypercent and less than about eighty percent of the exducer area. In yetanother example the port area of the exhaust gas bypass valve may begreater than about seventy-five percent and less than about eightypercent of the exducer area.

As is mentioned above, the exhaust gas bypass valve may be incorporatedinto a two-stroke engine. The exhaust gas bypass valve may be incommunication with the tuned pipe 47 and bypassing the turbochargerthrough a bypass pipe 136. The exhaust gas bypass valve 138 may becoupled to the center portion of the tuned pipe 47 The effective area ofthe port is determined using the diameter Pi shown in FIG. 6G andsubtracting the area of the valve member 614 and the axle 618.

Referring now to FIG. 10D, a plot of the ratio/percentage of exhaust gasbypass valve or bypass valve area to exducer area for known four strokeengines, two stroke engines and the present example are illustrated. Aswas observed, providing a higher ratio improved engine performance. Theratios or percentages may be used is four stroke and two stroke engines.From the data set forth is FIG. 10D, four stoke engines have a maximumratio of the port area to the exducer area of 0.5274 or 52.74 percentand for two stroke engines a 35.54 percentage port area to exducer areawas found.

Referring now to FIG. 11A, a portion of the controller 910 illustratedin FIG. 9A is set forth. One or more sensors 1110 are used to generatesensors signals that are communicated to a boost pressure set point1112. The sensors 1110 may include one or more of the sensorsillustrated in FIG. 9A such as the boost pressure sensor 912, the enginespeed sensor 914, the atmospheric pressure sensor 916, the throttleposition sensor 918, the tuned pipe pressure sensor 734, the exhaustvalve position sensor 937, the exhaust manifold pressure sensor 939 andthe denotation sensor 935. In particular, the sensors such as the enginespeed sensor 914, the throttle position sensor 918, the exhaust manifoldpressure sensor 939, the vehicle speed sensor 939A, the exhaust gastemperature sensor 939B,the exhaust valve position sensor 939C, and thepost compressor temperature sensor 939D may be used to determine a boostpressure set point. The measured boost pressure from the boost pressuresensor 912 is communicated to a summation block 1114. From this, a boosterror is determined.

Minimizing actuator movement at the boost target set point is importantfor engine performance because it creates a constant and predictableairflow through the bypass system for consistent engine speed andminimizes wear to the electronic actuator. A PID controller 1116 may bepart of the controller 910. The PID controller uses the boost error todetermine the gains to be used to change the position of the wastegateactuator. Ultimately, the gain Kp, Ki and Kd are determined at blocks1118, 1120 and 1122, respectively. The gains are determined from alook-up table 1124 in one example. Other examples for determining thegains are provided below. As set forth in more detail below, thedistance from the set point or a threshold or thresholds may be used tocompare to the boost error determined in the boost error determinationmodule 930. The gains determined in boxes 1118-1122 are used as part ofthe system transfer function 1130. Ultimately, the exhaust valveposition control module 934 uses the gains to determine an amount ofwastegate position change that is desired from the current position. Thechange of the wastegate position is ultimately measured by the boostpressure sensor error 912.

Referring now also to FIG. 11B, the boost pressure set point 1112 isillustrated graphically relative to a first boost pressure threshold1140 and a second boost pressure threshold 1142. The boost error may bea positive number or a negative number. That is, error is the boostpressure minus the target pressure. When the boost pressure is greaterthan the target value at a value above the threshold 1140, high gainsmay be provided. The high gain corresponds to a high wastegate positionchange. When the target pressure is much greater than the boostpressure, the value might be significantly negative and therefore pastor lower than the threshold 1142. A high gain with a high wastegateposition change may be provided. In the area between the first threshold1140 and the second threshold 1142, low wastegate change may beprovided. That is, only a small amount of wastegate position change maybe desired in the area between the thresholds 1140 and 1142. This helpsmitigate over-boost or over-shoot situations on a transient response.The system is used for a two stroke application in which it is desirableto have a fast response and stable actuator movement between near theset point. A typical PID controller may present an undesirable situationin trying to balance two competing requirements. The use of variablegains allows a more flexible pressure control loop to provide fastpressure response on transient situations while providing exceptionalPID control stability at the set point due to the reduced gains whichtranslate to smaller wastegate positions changes. The use of variablegains may also be gradual in the look-up table. That is, as the distancefrom the boost set point increases, the amount of change may increase inthe positive and negative directions. This control system also reducesthe need for individual term dead-bands near the set point because thegains can be brought to near zero to prevent cycling about the set pointon a highly unstable airflow system. The pressure stability is alsoincreased because undershoot and over compensation of PID control nearthe set point is prevented.

Referring now to FIG. 11C, a method of operating the system is setforth. In this example, the actual boost pressure is measured at step1150. In step 1152, the boost set point is determined. The boost setpoint may be determined from various sensors including sensorsindicative of the desired response from the system operator includingthe throttle position. In step 1154, the boost error is determined bycomparing or subtracting the actual boost pressure and the boost setpoint. After step 1154, three alternatives are provided for ultimatelychanging the wastegate position based upon the wastegate position changesignal as is determined. In step 1156, the wastegate position changesignal that is based on the boost error signal is derived from thelook-up table. As mentioned above, a low amount of gain or a low amountof wastegate position change is determined close to the set point. Afterstep 1156, the wastegate position based on the wastegate position changesignal is generated. Ultimately, the system continually repeats at step1150. In step 1158, the wastegate position may be based upon the amountof distance above or below a set point. The amount of wastegate positionchange may be directly calculated based upon the boost pressure amountabove or below a boost set point. This may be a linear or non-linearfunction. In step 1160, it is determined whether the boost error isgreater than a threshold. The boost error may be an absolute value ofthe boost error because the boost error may be above or below the setpoint, thus being a negative number. When the boost error is greaterthan the threshold, meaning above the first threshold 1140 or below thesecond threshold 1142 in step 1160, step 1164 determines the wastegateposition gain signal or the wastegate change signal accordingly. Itshould be noted that the thresholds 1140, 1142 may be differentdistances from the boost set point. Therefore, step 1160 may be replacedby determining whether the boost is above the first boost threshold 1140or below the set threshold 1142 illustrates in FIG. 11B.

When the boost error is not greater than the boost error threshold instep 1160, step 1166 applies less gain which is used in step 1164 tocalculate the wastegate position gain signal or the wastegate changesignal. After step 1164, step 1158 is again performed to determine thewastegate position that is based upon the amount of distance above orbelow a set point. The amount of wastegate position change may bedirectly calculated based upon the boost pressure amount above or belowa boost set point. Thereafter, step 1170 the wastegate position ischanged based upon the wastegate position change signal. Ultimately,this system continually repeats to reposition the wastegate based uponthe various sensors.

Referring now to FIG. 12A, turbocharged two-stroke engines createsubstantially more power in higher elevations than naturally aspiratedsnowmobile engines which leads to a more difficult operating experiencebecause the power delivery may be too much for an unskilled operator.Aftermarket turbocharger kits are difficult to handle in challengingsituations. Riders of different skill levels desire differentperformance characteristics so they do not feel overwhelmed. In thefollowing example, the controller 910 of FIG. 9A is illustrated infurther detail. For simplicity sake, the sensors 912-918, 734, 937, 939,935, 939A,939B, 939C, and 939D are not set forth but are incorporated byreference. In this example, an user interface 1212 is shown as a switch1214 that has various positions such as an off position, a sportposition, a performance position and a race position. Of course, thoseskilled in the art will recognize that the names and the number ofselectable features may be varied. In addition, a touch screen userinterface 1216 is illustrated. The touch screen user interface 1216includes touch screen button 1218A that corresponds to a sport mode,touch screen button 1218B that corresponds to a performance mode andtouch screen button 1218C that corresponds to a race mode. Of course,the touch screen interface may also include physcial buttons 1220A-1220Cthat correspond to the sport, performance and race modes, respectively.Further, a spearate “off” button may be provided. Of couse a secondselection of the touch screen buttons 1218A-C or physical buttons1220A-C may turn the particular mode off. As mentioned above, thewording or descriptors of the various modes and the number of modes maychange. Also, in a constructed example, one of the switch 1214, thetouch screen user interface 1216 or the physcial buttons 1220A-1220C maybe provided.

The user interface 1212 is coupled to the controller 910 through acontroller area network 1222. The controller area network communicatesthe signals corresponding to the switches that provides a mode signal tothe controller 910.

The controller 910 includes an idle module 1230 that determines whetherthe vehicle is idling. The idle module communicates signals to a boostfilter module 1232. A boost set point module 1234 and a scale module1236 communicates signals to the boost target module 1238. The boosttarget module 1238 communicates a signal to the boost error module 1240which, in turn, receives signals from the boost filter module 1232. Anovertemperature module 1242 may also be included within the controller910. The overtemperature module 1242 provides correction for thecondition where overtemperature is determined. An overboost module 1244provides the controller 910 with a correciton for overboost.

Referring now to FIG. 12B, a method for controlling the system accordingto the user selectable interface is set forth. In step 1250, thebarometric pressure is determined. In step 1251, the base target boostpressure is determined. In step 1252, it is determined whether aninterlock is engaged. When an interlock is engaged in step 1252, step1250 is again performed. The interlocks are set forth in steps1253A-1253F. Various types of interlocks may prevent the user interfaceselection from being used to control the vehicle. For example, 1253Aallows a limited ability user lock to be enabled. The limited abilityuser lock may be enabled by the user interface menus in which a limitedability user lock inteface code or password may be set. Without knowingthe password, the Imited ability lock may prevent the system from usingthe user selectable modes. The limited ability user lock may also bereferred to as a child lock. A password protection may also be providedin step 1253B. When a password is provided, the boost modes may not beselectable. Such a condition is suitable for the rental market in whichcertain modes may not be desirable for various users. In step 1253C,whether the throttle position sensor is generating a signal greater thanthe throttle position sensor interlock threshold is determined. That is,when the throttle position is high, meaning the throttle position isopened past an idle state or other threshold, the throttle positioninterlock threshold may prevent the system from being scaled accordingto the user interface. Likewise, in step 1253D, when the vehicle speedis greater than a vehicle speed interlock threshold, the scaling of theboost modes may not be performed. in step 1253E, the time may also be afactor for interlocking the system. That is, when the time is less thana time interlock threshold, the system may not allow for the user boostto be changed. In a similar manner, step 1253 prevents the user boostmode from activating when the absolute manifold pressure is greater thana pressure threshold. When at least one of the steps 1253A-1253F aretrue, the interlock is engaged. When the interlock is not engaged instep 1252, step 1254 receives a boost mode selection. As illustrated inFIG. 12A, the controller area network may provide the selection signalfrom the user interface. A boost mode scale factor is set in step 1255according to the selection signal. In step 1256, the target boost modebased upon the target boost and the boost modle scale factor isdetermined. In step 1257, the target boost correction is performed. Theexhaust bypass valve is controlled based upon the target boost in step1258.

Referring now to FIG. 12C, further details of the method for operatingis set forth. In this example, the barometric pressure is determined instep 1262A, the engine speed is determined in step 1262B and thethrottle position sensor signal that corresponds to the throttleposition is determined in step 1262C. The throttle position is used todetermine whether the idle mode is engaged. In step 1264, it isdetermined whether the idle modle entry conditions are determined basedupon the engine speed from step 1262B and the throttle position fromstep 1262C. After step 1264, step 1265 sets the parameter “Kboost” to 0indicating the system is at idle mode. Kboost is determined once atstartup and cleared when the engine is shut down.

In step 1266, determines the boost mode that is selected by the userinterface. The user selection from step 1266, the throttle position fromstep 1262C and the engine speed from step 1262B are provided through thecontroller area network 1222. The scaling factor from the sport module1268A, the performance module 1268B or the race module 1268C is providedto a boost scaling step 1270. The boost target base is determined instep 1271. The boost set point is determined in step 1272. The boost setpoint of step 1272 is determined from the boost target base in step 1271which is determined from the barometric pressure from step 1262A and theengine speed from step 1262B. Of course, other factors described belowmay be used to change the boost target base. Utlimately, the boostscaling from step 1270 and the boost set point from step 1272 arecombined in step 1273 and ultimately used to determine the boost targetin step 1274. The vehicle is controlled using the boost targetdetermined in step 1274.

Referring back to step 1265, the boost pressure readings in step 1276are zeroed based upon three consecutive raw boost determinations. Theboost pressure for idle uses the raw boost with the Kboost determined instep 1276. The boost pressure from step 1277 is used by step 1278 todetermine the boost filter value. The boost filter value in this exampleuses a number of sample values from step 1277. In step 1279, the numberof values used in step 1278 is provided. A differential block 1280receives the filtered boost pressure and the target boost pressure instep 1274 to determine a boost pressure error in step 1281. Thedifference between the boost target pressure of step 1274 and the boostfilter value of step 1278 that is calculated versus the scale boostvalue determines the boost error in step 1281.

It should be noted that when the boost scaling is performed in step1270, the amount of scaling varies depending upon the user's selections.The amount of scaling may, for example, take place as a percentage ofthe set point.

Referring now to FIG. 13A, the operation of the overboost module 1244 ofFIG. 12A is set forth. In FIGS. 13A and 13B, the control of the engineto prevent overboost or high post-compressor temperatures is set forth.This allows the engine to be protected without being very intrusive.That is, abrupt changes in the boost level are avoided. The low inertiaand low weight of a snow vehicle is significantly impacted by the amountof power delivery of the engine. Abrupt changes in the amount of powerprovided leads to a feeling of instability and may ultimately lead tothe vehicle being stuck.

In step 1310, the target boost is determined. As mentioned above, thetarget boost may be determined as described in reference to FIGS. 12Band 12C. In step 1312, the actual boost pressure is measured by apressure sensor. In step 1314, when the boost pressure is greater thanthe target boost multipled by a first overboost factor, step 1316 isperformed. When the boost pressure is not greater than the target boostwith the overboost factor, step 1312 is performed. The overboost factoris a predetermined amount that is calibratable by the system designer.The overboost factor is a numeric factor that allows the boost pressureto exceed the target boost by a predetermined amount. The overboostfactor may be greater than one so that the target boost may be exceededby a predetermined amount or percentage.

In step 1316, a timer is started. When the timer is greater than a firstthreshold in step 1318, step 1320 positions the wastegate to acalbriatable position in step 1320. In step 1322, a calibratable timedelay is waited.

In step 1324, if the boost pressure is not greater than the target boostwith the overboost factor, step 1310 is again performed. In step 1324when the boost pressure is greater than the target boost multiplied by asecond overboost factor, step 1326 resets the timer and initiates thesecond timing process. The second overboost factor may be different thanthe first overboost factor of step 1314. In step 1328, if the timer isgreater than a second timer threshold, step 1330 changes the position ofthe exhaust bypass valve or wastegate. The timer in step 1316 and 1326allow a predetermined amount of time to pass before the values arechanged. In step 1330, the amount of opening of the exhaust bypass valveor wastegate is changed. This may vary depending upon the differencebetween the boost pressure and the target boost or the target boost withthe overboost factor. In step 1332, an overboost warning may be providedafter the second attempt to change the boost pressure. The time delay instep 1322 and step 1326 is calibratable so that the air flow to theengine and therefore the power output of the engine has enough time toshow some change. This allows the engine to be protected without beingintrusive to the rider or leaving the rider stranded.

Referring now to FIG. 13B, a method for operating the overtemperaturemodule 1242 of FIG. 12A is set forth. In this example, the target boostis determined in step 1340. In step 1342, the maximum post compressortemperature as a function of the target boost is determined. This may bea calibated factor determined duriing development that may provided in alookup table. In step 1344, the actual post compressor temperature isdetermined. The post compressor temperature may be determined by thepost compressor temperature sensor 939D illustrated in FIG. 9A. In step1346, the actual post compressor temperature is compared to the maximumpost compressor temperature threshold. When the actual post compressortemperature is not greater than the maximum post compressor temperaturethreshold, step 1340 is again performed. In step 1346, when the actualpost compressor temperataure is greater than the maximum post compressortemperature threshold, step 1348 is performed in which a timer isstarted. In step 1350, the timer value is compared to a first timethreshold. When the timer is greater than the first time threshold instep 1350, step 1352 reduces the target boost and resets the timer instep 1354. A counter is incremented in step 1356. When the counter isnot greater than a counter threshold, step 1346 is again performed. Instep 1358, when the counter is greater than the counter threshold, step1360 commands the wastegate to a calibratable position. In step 1362,the electronically controlled engine exhaust valve or valves on amulticylinder engine is commanded to a calibratable position. In step1364, an overtemperature warning is generated. The overtemperaturewarning may be an indicator light provided on the display of thevehicle. In the foregoing example, the first response loop continues forthe calibratable number of loops and can continuously drop the targetboost pressure until either the post compressor temperature drops belowthe above mentioned calibratable limit or the loop count reaches acalibratable value. When the loop count reaches the calibratable value,the system enters a second state of response in which the wastegatevalve is commanded to a calibratable position and the exhaust valves ofthe engine are commanded to a calibratable position to protect theengine.

Referring now to FIG. 14A, a method for controlling the wastegate duringdeceleration of the vehicle is set forth. In the following example, thewastegate position is moved based upon the throttle position or the rateof change of the throttle or both. The method purposely opens thewastegate prior to a condition of overboost and may more fully open thewastegate than in an overboost condition as described above in FIG. 13A.This allows the overboost condition to be reduced and prevents poorscavenging through the engine that is caused by high exhaust pressure.Poor scavenging causes poor running quality and possible knock ordenotation, or hesitation.

In step 1410, the throttle position is determined. in step 1420, therate of change of the throttle position is determined. In step 1422, theengine speed is determined. A boost level is determined in step 1424.The boost level may be determined in various ways including that setforth in FIGS. 12A-12C. In step 1426, the commanded wastegate positionis determined based upon the engine speed and the boost level. In step1428, a correction factor is determined based on the throttle arate ofchange or the throttle position

In FIG. 14B, the wastegate opens slightly based on an overboostcondition in the region set forth in the area circled by the area 1440.The area 1440 circled is the throttle position sensor signal 1442. Theengine speed is signal 1444 and the boost pressure is 1446. Thewastegate actuator position is signal 1448. In FIG. 14C, the wastegateactuator position illustrated by signal 1448 is purposely driven to morefully open based upon the declining engine speed represented by thesignal 1444. As can be seen by contrasting FIGS. 14B and 14C, the boostpressure 1446 does not obtain such a high level as that illustrated inFIG. 14B.

Referring now to FIG. 15A, one drawback to turbocharged snowmobiles isthe time delay associated with the turbocharger building boost for theengine to accelerate. The use of a bypass control wastegate creates aparallel path from the tuned pipe to the silencer that allows forsignificant improvements in the off boost engine speed response.However, under very fast transients when the pipe pressure remains highand the turbocharger speed is low, the engine response requires adifferent amount of bypass airflow then it would during a slowertransient response. In the following method, a two-stage specificwastegate control based on the engine speed and the boost error are useduntil the engine has reached a target boost set point.

In step 1510, the barometric pressure is determined from a barometricpressure sensor. In step 1512, the engine speed is generated from anengine speed sensor. In step 1514, the throttle position is determinedfrom a throttle position sensor. In step 1516, the boost pressure isdetermined from a boost pressure sensor. It should be noted that step1510 through 1516 are continually performed during the operation of theengine. In step 1518, the boost offset of Step 1520 is performed oncewhen the engine is in an idle state upon power up of the enginecontroller (ECU) and stored therein. In step 1520, the boost offset isdetermined in a similar manner to that described above. The boost offsetis used for zeroing using an average to get (Kboost). In step 1522, theboost offset and the raw boost from step 1516 are used together with abarometric pressure to determine the boost pressure. That is, the rawboost with the offset removed and the barometric pressure removed isused to obtain the boost pressure. A filtered boost pressure isdetermined in step 1524 which uses a number of boost pressure readings.That is, a number of samples may be averaged for the boost pressurereading to obtain the filtered boost pressure reading. In step 1526, ascale factor may be determined from the user settings as described abovein FIGS. 12A-12C. In step 1528, a target boost from the boost scaling isgenerated. In step 1530, the boost offset is used to obtain the boosttarget. The fuel mode may also be used for changing the boost target instep 1532. Depending upon the type of fuel, a lookup table may be usedfor determining a fuel mode correction. In step 1534, a detonationfactor may be used to adjust the boost target. In step 1536, a boosterror, which is the filtered boost minus the target boost, isdetermined. In step 1538, based upon engine speed and the throttleposition, a launch mode is determined. Launch mode is determined basedupon the engine speed and the throttle position. This may be performedby referring to a table using a one or zero that defines whether the PIDcontrol of the wastegate is active at the operating point. In step 1540,it is determined what the rate of change of the throttle position sensoris. In step 1542, when the throttle position rate of change is greaterthan a throttle position rate of change threshold, step 1544 isperformed. When the throttle position rate of change is not greater thanthe throttle position rate of change threshold, step 1510 is performed.In step 1544, when the launch state is not active, step 1510 isperformed. When the launch state is active, the fixed position PIDcontrol is enabled. This is in contrast to when the boost error PID modeis activated. Thus, when the fixed position PID control is activated,the launch state is active and step 1546 is performed. Step 1546determines whether the boost pressure is less than the target boosttimes a scale factor. Thus, when all three conditions of steps 1542-1546are performed, step 1550 enters a first stage of acceleration mode. Thewastegate enters a fixed position PID control stage that controls thewastegate position to a desired percentage opened based upon the enginespeed and the boost error in step 1552. In step 1554, a timer isinitiated. In step 1556, when the timer period has not expired, step1556 is again performed. In step 1556, when the time has expired, step1558 is performed to determine the target boost from a second map basedupon the engine speed and boost error. In step 1560, the boost pressureis determined. In step 1562, if the boost pressure is below the targetboost pressure multiplied by a scaling factor, then a second stage PIDcontrol mode is entered in step 1564. The second stage will be activatedas long as the condition in step1562 is true. In the second stage of1564, step 1566 controls the wastegate to a calibratable percentageopened based upon the engine speed and the boost error. A separatecontrol map different than the control map used in the first stage maybe used. The control maps are determined during the development process.By implementing the multi-stage acceleration function, fast engine andturbocharger response is created and thus faster acceleration isachieved. Quicker acceleration for normally aspirated engines isachieved during a high rate of transients. The drivability of such asystem in high-speed throttle drop conditions, which are common in treeriding, is achieved. Smoother transitions from a fixed state PID controlto a boost pressure PID is achieved. The flexibility for accelerationcontrol with distinct maps between stages is also achieved. Thetransition from the second stage boost PID to a target boost scalingconditional parameter in the second stage is performed while in theloop. A reduction in underboost condition is also achieved with lowinitial turbocharger speeds. Referring now to FIG. 15C, the engine speedsignal is signal 1570. The throttle position is signal 1572. The boostpressure is signal 1574 and the wastegate position is 1576. The variousstages of wastegate control are illustrated. A first region 1578 shows afirst stage control. Region 1580 is controlled by the second stage.Region three is controlled in a PID mode at 1582.

Referring now to FIGS. 16A and 16B, a connecting rod 1610 is illustratedhaving a shank 1612 having a first bearing bore 1614 and a secondbearing bore 1616, the first bearing bore 1614 has a first rollerbearing 1618 disposed therein. A second roller bearing 1620 is disposedin the second bearing bore 1616. A description of one suitable exampleof a roller bearing is set forth below.

The shank 1612 has a first web portion 1622, a second web portion 1624and a center portion 1626 disposed between the first web portion 1622and the second web portion 1624. As is best illustrated in FIG. 16B, thethickness of the center portion 1626 is less than the thickness of thefirst web portion 1622 and the second web portion 1624. A first hole1628A is disposed through the center portion 1626 adjacent to wall 1630defining the first bearing bores 1614. A second hole 1628B is disposedwithin the center portion 1626 adjacent to the wall 1632 that definesthe second bearing bore 1616. The holes reduce the stiffness near thebores, which balances the bearing roller forces to improve bearing life.Since the stiffness of the connecting rod 1610 at each end near thebores are difficult to affect with forging geometry changes, a machinedhole or a plurality of holes after forging allows the desired stiffnessto be achieved. The reduced stiffness in the shank near the borebalances the bearing roller forces and reduces the peak roller forceduring a compressive load due to distortion of the bearing bore. Highroller forces in a needle roller bearing used in a connecting rod of atwo-stroke engine causes spalling as well as overheating of the bearing.The high roller forces are due to the connecting rod stiffnesspreventing it from conforming to the shape of the bearing with anecessary clearance, which loads some rollers much more than others. Thestiffness of the connecting rod in each end of the bore is difficult toaffect with forging geometry changes. Ultimately, the reduction instiffness causes the bearings to have increased life. The holes alsoreduce the connecting rod mass, which is highly desirable. The size andthe location of the holes may be changed to balance the roller forcesand optimize the weight.

Referring now to FIG. 16C, a combustion event having the forces on theroller bearing is illustrated. Plot 1650 shows roller forces on aconnecting rod without a hole. Plot 1652 shows the plot of the rollerforces with the holes. The peak roller force is thus reduced by markinga comparison and the forces are more balanced around the perimeter ofthe bearing bore.

Referring now to FIG. 16D, a plot of the inertia direction forceswithout the holes illustrated by lines 1654 and with the holesillustrated by lines 1656 are nearly identical and thus the inertiadirection forces are unchanged.

Referring now to FIG. 17, a roller bearing 1710 suitable for use asroller bearing 1618 or 1620 of FIG. 16A is set forth. The rollerbearings 1710 may be three dimensionally metal printed in a first halfand a second half. The roller bearing 1710 has a cage 1712 with aplurality of longitudinal extending slots 1714. The longitudinallyextending slots 1714 do not extend all the way to the furthest width orends of the cage 1712. The cage may be printed with the needle rollers1720 incorporated therein. This allows the needle roller 1720 to beencapsulated in the cage with no additional processing required. Holes1722 through the space or longitudinally extending walls 1724 allow oilto pass through the cage. The cage 1712 may also be printed in halvesfor split rod bearing designs. Hollow sections are used to reduce theweight of the bearing with the process. The steel cage 1712 may bethinly coated with copper or silver during the printing process toreduce friction on all the surfaces. This eliminates the need forfurther processing or coating of the part after it is formed. Asmentioned above, the needle roller bearing cage 1712 may be used invarious locations on a vehicle, especially in a two-stroke engines whereneedle roller bearings are typically used.

In previous roller bearings with stamped bearing cages, the cage wascrimped to encapsulate the rollers. Deformation caused by the processaffected the roundness of the cage. The present process ofthree-dimensional printing reduces the deformation of the bearing cage.The lubricating holes allow more oil to pass through the bearing andincrease the life of the bearing.

Referring now to FIG. 18, the controller 910 of FIG. 9A is illustratedwith different modules disposed therein. In this example, the controller910 is coupled to various sensors including all of the sensorsillustrated in FIG. 9A. In this example, all of the sensors are notspecifically illustrated. The throttle position sensor 918 isillustrated, the wastegate position sensor 939C, a boost pressure sensor912, engine speed sensor 914, the atmospheric or barometric pressuresensor 916, the tuned pipe pressure sensor 734 and other sensors 1810including the other sensors set forth in FIG. 9A.

The controller 910 includes controller 1812, a wastegate initializermodule 1814 a fuel adjustment module 1816 and a sensor diagnostic module1818. The exhaust valve controller 1812 controls the position of theelectronically controlled exhaust valve 49. The wastegate initializer1814 is used to initialize the position of the wastegate to zero out anyinconsistencies. The wastegate initializer 1814 may generate a screendisplay such as an indicator light or a display on the touch screen atthe display 1820. The fuel adjustment module 1816 performs fuel amountadjustments in response to one or more of the boost pressure, thebarometric pressure, the engine speed and the throttle position asdetermined by the sensors.

The sensor diagnostic module 1818 may generate a service flag 1822 andgenerate an indicator on the display 1820. The service flag 1822 may beset within the software of the system.

A memory 1830 stores various parameters and calibratable data therein.In this example, wastegate values 1832 are stored within the memory. Aswell, a table having boost box pressure and throttle position fordetermining the position of an electronically controlled exhaust valveis set forth in the memory portion 1834. The modules 1812 through 1818are described in further detail below.

Referring now to FIG. 19, a method of operating the engine, and inparticular the exhaust valve controller 1812 of FIG. 18 is set forth.The method of FIG. 19 may be performed in engines with or without aturbocharger. In the following method, a method for controlling theelectronically controlled exhaust valves of the engine is set forth. Thethrottle position and the absolute air box or boost box pressure is usedto determine the engine speed at which the exhaust valve controller 1812commands the electronically controlled exhaust valve 49 to move.

In step 1910, the boost box pressure is determined. The boost boxpressure takes into consideration the turbocharger boost if in aturbocharged engine and the barometric pressure, each of which arepresent within the boost box. In step 1912, the throttle position isdetermined. The throttle position is determined from the throttleposition signal. Typically, the throttle position is a percentage of theamount that the throttle is opened. In step 1914, the engine speed fromthe engine speed sensor is determined. Typically, the engine speed is avalue corresponding to the rotational speed of the crankshaft. In step1916, the boost box pressure signal and the throttle position signal areused to determine the engine speed at which to trigger the opening ofthe exhaust valve. In step 1918 when the engine speed reaches the enginespeed trigger or is greater than the engine speed trigger step 1920opens the exhaust valve. In step, 1918 when the engine speed is notgreater than the engine speed trigger the system repeats in step 1910.As mentioned above, step 1916 uses a two-dimensional boost box/throttleposition table such as that illustrated in FIG. 18 as reference numeral1834. By controlling the movement of the electronically controlledexhaust valve of the engine based upon the boost box pressure, thevarying elevation and how the engine runs due to the differentbarometric pressures is taken into consideration. Thus, a smoother andbetter operating engine is achieved.

Referring now to FIG. 20, a method for checking the wastegate or exhaustbypass valve is set forth. The wastegate is placed in a parallel flowpath to the turbocharger and has an upper and lower mechanical stop thatare learned for accurate control of the wastegate. The lower mechanicalstop and upper mechanical stop are learned by the controller 910 usingthe wastegate initializer 1814 described above. Essentially, the voltagereadings at each stop are learned. The following method allows thevoltages at each stop to be learned, stored and used during operationand compared to determine whether the voltages are out of range so thatan indicator may be generated to the vehicle operator.

In step 2010, the system determines whether the vehicle has started.When the vehicle has started, step 2012 determines if the engine speedis greater than an exhaust bypass valve position check threshold. Whenthe engine speed is greater than an exhaust bypass valve position checkthreshold step 2016 is performed. In step 2012 when the engine speed isnot greater than the check threshold step 2010 is repeated. In step2014, the position of the valve is determined by reading the throttleposition sensor voltage. In step 2016, the exhaust bypass valve iscommanded to the upper mechanical stop. In step 2018, the engine speedsensor and throttle position sensor are checked if they are less than anidle state threshold. If the throttle position value or engine speedvalue is above the threshold the sensor outputs continually read in step2018. When the throttle position sensor value and engine speed value arebelow the idle state threshold step 2020 stores the voltage value at theupper electrical stop. In step 2022 it is determined whether the uppermechanical stop value is greater than an upper voltage threshold. Step2024 generates a warning signal such as an indicator or audible signalat the vehicle display. In step 2022 when the upper mechanical stopvalue is not greater than an upper voltage threshold step 2026 commandsthe exhaust bypass valve to a lower mechanical stop. In step 2028 thethrottle position sensor value is read. That is, the voltage ismonitored in step 2028. In step 2030 the throttle position sensor valueand engine speed sensor value are monitored to determine they are lessthan an idle state threshold. When the values are not below an idlestate threshold step 2028 is again performed. When the throttle positionsensor value and engine speed value are below the idle state threshold,step 2032 stores the lower electrical stop voltage value. After step2032, step 2034 determines whether the lower mechanical stop value isless than a lower voltage threshold. When the lower mechanical stopvalue is not less than the lower mechanical voltage threshold, step 2010is again performed. In step 2034 when the lower mechanical stop value isless than a lower voltage threshold a warning signal is generated instep 2024.

Referring now to FIG. 21, a method for monitoring the current duringstartup is set forth. In step 2110 the current during the startup checkperformed in FIG. 20 is monitored. When the wastegate or exhaust bypassvalve actuator current is higher than a high current threshold step 2114generates a cleaning check warning. A high current may be generated whenthe system is encumbered by snow, ice or other debris.

In step 2112 when the wastegate actuator current or exhaust gas bypassvalve current is not greater than a high threshold the wastegateactuator current is compared to a low current threshold in step 2120.When the wastegate current is not below a low threshold current step2110 is again performed. When the wastegate actuator current is greaterthan a low current threshold step 2122 causes the engine controller 910to enter a limp home mode and thereafter step 2124 generates a mechanismerror signal and optionally a warning display.

The methods set forth in FIGS. 20 and 21 allow the wear to the wastegateto be monitored which can impact the current consumption of the actuatorand change the airflow characteristics of the wastegate or exhaust gasbypass valve with regard to the control position. The system also allowsthe interface between the electrical actuator output shaft and thewastegate rotating assembly to be monitored. In some instances wear canlead to chatter in an otherwise stable system. Ice buildup or otherdebris on the rotating assembly can be monitored. When debris or icebuildup occurs, a slow response of the wastegate can cause an overshootof the system because the system tries to correct for the response timebased on the undershoot. Corrections in FIG. 20 using the voltage, thesystem may be continually monitored for out of range values.

Referring now to FIG. 22, a method for controlling a fuel and ignitionsystem for fueling and controlling the timing of ignition of the engineis set forth. In step 2210 the boost pressure for the engine isdetermined. In step 2212 the throttle position desired for the engine isalso determined. In step 2214 the exhaust bypass valve position isdetermined. In step 2216 the fuel ignition amount based upon the exhaustbypass valve position is generated. The amount of fuel for the fuelsystem is determined during development of the engine. The fuel andignition are also a function of the boost pressure at the specificthrottle position. However, in conjunction with the exhaust bypass valveposition, the engine speed may be maintained at a more stable position.

Referring now to FIG. 23, wastegate position signal 2240 is shown havingan abrupt drop which causes the engine speed signal 2242 to rapidlyincrease then decrease. The rapid increase and decrease are shown aswell at the boost pressure signal 2244. The throttle position signal2246 as can be seen is maintained in the region of the wastegateposition signal rapidly decreasing. By controlling the fueling and thespark the engine RPM may have the upward spike and downward spikeeliminated as illustrated by the dashed line 2248.

Referring now to FIG. 24, the method for diagnosing a turbochargersystem is set forth. In this example, production pressure sensors thatare mass-produced have various tolerances. The barometric pressuresensor and the boost pressure sensor may have different readings whenexposed to the same pressures. The present system allows the differenceto be set to zero in the control software. However, there is also acheck for the diagnosing of a sensor failure. The following is performedat idle. In step 2408 it is determined whether the engine is at idlestate. If the system is not step 2408 is performed. If the engine is atidle in step 2408, step 2410 is performed. In step 2410, the boostpressure after the turbocharger is determined. This is determined from aboost pressure signal generated from a boost pressure sensor that isdisposed downstream of the turbocharger compressor. In step 2412, thebarometric pressure is determined from a barometric pressure sensor thatis disposed before the turbocharger. In step 2414, a pressure sensoroffset value between the barometric pressure signal and the boostpressure signal is determined by comparing the barometric pressure andthe boost pressure signal. In step 2416, it is determined whether thepressure sensor offset is outside a tolerance. The tolerance may have athreshold 2440 and 2442 as illustrated in FIG. 25. When the pressuresensor offset is outside of the tolerance meaning outside of the sensoracceptable tolerance range as defined by thresholds 2440 and 2442, aservice flag may be set in the software in step 2418. Also, a vehicledisplay is generated in step 2420. One example of a vehicle display isthat set forth as the display 2450 of FIG. 25. A red indicator may begenerated when the difference between the boost pressure and thebarometric pressure are outside of the range. It should be noted thatthe system measures the boost pressure and barometric pressure in steps2410 and 2412 upon startup of the engine when no boost pressure from theturbocharger is being generated. In this state both the boost pressureand the barometric pressure should be identical. The engine may beallowed to operate in a limited manner in a limp home mode to allow thevehicle operator to seek help. When the offset is within the range, theboost pressure is corrected by the offset value and the engine operatesusing corrected boost pressure in step 2422. After step 2422, the methodrestarts in 2408.

The foregoing description has been provided for purposes of illustrationand description. It is not intended to be exhaustive or to limit thedisclosure. Individual elements or features of a particular example aregenerally not limited to that particular example, but, where applicable,are interchangeable and can be used in a selected example, even if notspecifically shown or described. The same may also be varied in manyways. Such variations are not to be regarded as a departure from thedisclosure, and all such modifications are intended to be includedwithin the scope of the disclosure.

1-10. (canceled)
 11. A system for controlling an engine having aturbocharger comprising: a boost pressure sensor generating a boostpressure signal; a barometric pressure sensor generating a barometricpressure signal; and a controller coupled to the boost pressure sensorand the barometric pressure sensor, said controller programmed todetermine an offset between the boost pressure signal and the barometricpressure signal, when the offset is outside a tolerance range, displayan indicator.
 12. The system of claim 11 wherein the controller isprogrammed to operate the engine based on the offset when the offset iswithin the tolerance range.
 13. The system of claim 11 wherein thecontroller is programmed to correct a boost pressure signal using theoffset determined by comparing the barometric pressure signal and theboost pressure signal prior to operating the engine.
 14. The system ofclaim 11 wherein the boost pressure sensor is disposed after aturbocharger compressor.
 15. The system of claim 11 wherein thebarometric pressure sensor is disposed before a turbocharger compressor.16. A method for controlling an engine having a turbocharger comprising:generating a boost pressure signal; generating a barometric pressuresignal; and a controller programmed to determine an offset between theboost pressure signal and the barometric pressure signal, display anindicator when the offset is outside a tolerance range.
 17. The methodof claim 16 further comprising when the offset is within the tolerancerange, operating the engine based on the boost pressure signal correctedby the offset.
 18. The method of claim 16 further comprising correctingthe boost pressure signal using the offset prior to operating the enginebased on the corrected pressure value.
 19. The method of claim 16wherein generating the boost pressure signal comprises generating theboost pressure signal from a boost pressure sensor disposed after aturbocharger compressor.
 20. The method of claim 16 wherein generatingthe barometric pressure signal comprises generating the barometricpressure signal from a barometric pressure sensor disposed before aturbocharger compressor. 21-22. (canceled)